script: track per-script theme contributions and purge on script unload

Make individual scripts the unit of ownership for theme contributions
so that loading a script that calls weechat.theme_register(...) and
later unloading it correctly removes the script's overrides.

Plugin API addition (weechat-plugin.h):

  - new function pointer t_weechat_plugin.theme_unregister_script
    delegates to core's theme_unregister_script.
  - new convenience macro weechat_theme_unregister_script(script).
  - WEECHAT_PLUGIN_API_VERSION bumped to 20260527-02.

Script API additions (plugin-script-api.{c,h}):

  - new plugin_script_api_theme_register (plugin, script, name,
    overrides) forwards to the plugin API with the script pointer
    as the contribution owner, so contributions are tracked
    per-script (not per script-language plugin).

Lifecycle wiring (plugin-script.c):

  - new file-local plugin_script_remove_themes (plugin, script)
    calls weechat_theme_unregister_script.
  - plugin_script_remove now calls it alongside the other
    plugin_script_remove_* helpers, so script-unload tears down
    everything (configs, bar items, themes, hooks).

Eight language bindings updated to call
plugin_script_api_theme_register instead of weechat_theme_register
directly, so they pass the script pointer as owner:

  - python, perl, ruby, lua, tcl, javascript, php, guile.

The behavior change is end-to-end visible only at script unload:
before, an unloaded script's theme overrides lingered in the
registry forever and would be re-applied on the next /theme apply;
after, they vanish when the script unloads. /plugin unload of an
entire script-language plugin already worked via commit 24's hook
in plugin_remove (which drops both plugin-only contributions and
their script-owned children when the language plugin itself goes
away, because the contribution's plugin pointer matches).

No new unit tests in this commit: the underlying theme_unregister_script
function is covered by TEST(CoreTheme, UnregisterByOwner), and the
remaining changes are plumbing.

src/plugins/guile/weechat-guile-api.c

@@ -2019,8 +2019,10 @@ weechat_guile_api_theme_register (SCM name, SCM overrides)
                                                     WEECHAT_HASHTABLE_STRING,
                                                     WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register (API_SCM_TO_STRING(name),
-                                                 c_overrides));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_guile_plugin,
+                             guile_current_script,
+                             API_SCM_TO_STRING(name), c_overrides));
 
     weechat_hashtable_free (c_overrides);
 

src/plugins/javascript/weechat-js-api.cpp

@@ -1912,7 +1912,10 @@ API_FUNC(theme_register)
         WEECHAT_HASHTABLE_STRING,
         WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register (*name, hashtable));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_js_plugin,
+                             js_current_script,
+                             *name, hashtable));
 
     if (hashtable)
         weechat_hashtable_free (hashtable);

src/plugins/lua/weechat-lua-api.c

@@ -2097,7 +2097,10 @@ API_FUNC(theme_register)
                                          WEECHAT_HASHTABLE_STRING,
                                          WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register (name, hashtable));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_lua_plugin,
+                             lua_current_script,
+                             name, hashtable));
 
     weechat_hashtable_free (hashtable);
 

src/plugins/perl/weechat-perl-api.c

@@ -2017,7 +2017,10 @@ API_FUNC(theme_register)
                                                 WEECHAT_HASHTABLE_STRING,
                                                 WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register (name, hashtable));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_perl_plugin,
+                             perl_current_script,
+                             name, hashtable));
 
     weechat_hashtable_free (hashtable);
 

src/plugins/php/weechat-php-api.c

@@ -2194,8 +2194,10 @@ API_FUNC(theme_register)
                                                 WEECHAT_HASHTABLE_STRING,
                                                 WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register ((const char *)name,
-                                                 overrides));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_php_plugin,
+                             php_current_script,
+                             (const char *)name, overrides));
 
     weechat_hashtable_free (overrides);
 

src/plugins/plugin-script-api.c

@@ -1568,6 +1568,28 @@ plugin_script_api_config_unset_plugin (struct t_weechat_plugin *weechat_plugin,
     return return_code;
 }
 
+/*
+ * Register theme overrides on behalf of a script.
+ *
+ * Forwards to weechat_plugin->theme_register with the script pointer
+ * as the owner, so the contribution can be auto-purged when the
+ * script unloads (see plugin_script_remove_themes).
+ */
+
+struct t_theme *
+plugin_script_api_theme_register (struct t_weechat_plugin *weechat_plugin,
+                                  struct t_plugin_script *script,
+                                  const char *name,
+                                  struct t_hashtable *overrides)
+{
+    if (!script)
+        return NULL;
+    return (weechat_plugin->theme_register) (weechat_plugin,
+                                             script,
+                                             name,
+                                             overrides);
+}
+
 /*
  * Create an upgrade file.
  *

src/plugins/plugin-script-api.h

@@ -438,6 +438,10 @@ extern void plugin_script_api_config_set_desc_plugin (struct t_weechat_plugin *w
 extern int plugin_script_api_config_unset_plugin (struct t_weechat_plugin *weechat_plugin,
                                                   struct t_plugin_script *script,
                                                   const char *option);
+extern struct t_theme *plugin_script_api_theme_register (struct t_weechat_plugin *weechat_plugin,
+                                                         struct t_plugin_script *script,
+                                                         const char *name,
+                                                         struct t_hashtable *overrides);
 extern struct t_upgrade_file *plugin_script_api_upgrade_new (struct t_weechat_plugin *weechat_plugin,
                                                              struct t_plugin_script *script,
                                                              const char *filename,

src/plugins/plugin-script.c

@@ -1080,6 +1080,18 @@ plugin_script_free (struct t_plugin_script *script)
     free (script);
 }
 
+/*
+ * Remove all theme contributions registered by this script.
+ */
+
+void
+plugin_script_remove_themes (struct t_weechat_plugin *weechat_plugin,
+                             struct t_plugin_script *script)
+{
+    weechat_theme_unregister_script (script);
+    (void) weechat_plugin;  /* used implicitly via the macro */
+}
+
 /*
  * Remove a script from list of scripts.
  */
@@ -1101,6 +1113,8 @@ plugin_script_remove (struct t_weechat_plugin *weechat_plugin,
 
     plugin_script_remove_configs (weechat_plugin, script);
 
+    plugin_script_remove_themes (weechat_plugin, script);
+
     /*
      * remove again all hooks created by this script (just in case new hooks
      * were created by the calls above)

src/plugins/plugin.c

@@ -801,6 +801,7 @@ plugin_load (const char *filename, int init_plugin, int argc, char **argv)
         new_plugin->config_unset_plugin = &plugin_api_config_unset_plugin;
 
         new_plugin->theme_register = &theme_register;
+        new_plugin->theme_unregister_script = &theme_unregister_script;
 
         new_plugin->key_bind = &gui_key_bind_plugin;
         new_plugin->key_unbind = &gui_key_unbind_plugin;

src/plugins/python/weechat-python-api.c

@@ -2019,7 +2019,10 @@ API_FUNC(theme_register)
                                                   WEECHAT_HASHTABLE_STRING,
                                                   WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register (name, hashtable));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_python_plugin,
+                             python_current_script,
+                             name, hashtable));
 
     weechat_hashtable_free (hashtable);
 

src/plugins/ruby/weechat-ruby-api.c

@@ -2498,7 +2498,10 @@ weechat_ruby_api_theme_register (VALUE class, VALUE name, VALUE overrides)
                                                   WEECHAT_HASHTABLE_STRING,
                                                   WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register (c_name, c_overrides));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_ruby_plugin,
+                             ruby_current_script,
+                             c_name, c_overrides));
 
     weechat_hashtable_free (c_overrides);
 

src/plugins/tcl/weechat-tcl-api.c

@@ -2051,7 +2051,10 @@ API_FUNC(theme_register)
                                                WEECHAT_HASHTABLE_STRING,
                                                WEECHAT_HASHTABLE_STRING);
 
-    result = API_PTR2STR(weechat_theme_register (name, hashtable));
+    result = API_PTR2STR(plugin_script_api_theme_register (
+                             weechat_tcl_plugin,
+                             tcl_current_script,
+                             name, hashtable));
 
     weechat_hashtable_free (hashtable);
 

src/plugins/weechat-plugin.h

@@ -77,7 +77,7 @@ struct t_weelist_item;
  * please change the date with current one; for a second change at same
  * date, increment the 01, otherwise please keep 01.
  */
-#define WEECHAT_PLUGIN_API_VERSION "20260531-01"
+#define WEECHAT_PLUGIN_API_VERSION "20260531-02"
 
 /* macros for defining plugin infos */
 #define WEECHAT_PLUGIN_NAME(__name)                                     \
@@ -734,6 +734,8 @@ struct t_weechat_plugin
                                        const void *script,
                                        const char *name,
                                        struct t_hashtable *overrides);
+    void (*theme_unregister_script) (struct t_weechat_plugin *plugin,
+                                     const void *script);
 
     /* key bindings */
     int (*key_bind) (const char *context, struct t_hashtable *keys);
@@ -1866,6 +1868,8 @@ extern int weechat_plugin_end (struct t_weechat_plugin *plugin);
 #define weechat_theme_register(__name, __overrides)                     \
     (weechat_plugin->theme_register)(weechat_plugin, NULL,              \
                                      __name, __overrides)
+#define weechat_theme_unregister_script(__script)                       \
+    (weechat_plugin->theme_unregister_script)(weechat_plugin, __script)
 
 /* key bindings */
 #define weechat_key_bind(__context, __keys)                             \