fix(fonts): unloading a plugin forgets its manifest fonts (#757)

* fix(fonts): unloading a plugin forgets its manifest fonts

PluginManager.unload_plugin() and the failed-load cleanup only called
FontManager.forget_manager_fonts(), which drops usage data. The plugin's
manifest registrations stayed: plugin_fonts / plugin_font_catalogs, its
plugin_id::family entries in font_catalog, and cached font objects for them
-- so its fonts kept resolving after unload and a family a reinstalled
manifest dropped stayed registered. The deprecated unregister_plugin_fonts
did this cleanup but nothing called it; it was removed in #708.

Add FontManager.forget_plugin_fonts(plugin_id) and call it from both
paths alongside forget_manager_fonts (each guarded on its own, so a font
manager stub with only one still works). FontManager takes no locks, so
like forget_manager_fonts it uses atomic pops over snapshots. A reload
(unload + load) registers the manifest fonts again and they resolve.

Raised by CodeRabbit on #709.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(fonts): call the font manager's forget methods without a None-able local

Pylint E1102 (Codacy) read getattr(..., None) as possibly not callable.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

src/font_manager.py

@@ -222,6 +222,39 @@ class FontManager:
             logger.error(f"Error registering fonts for plugin {plugin_id}: {e}", exc_info=True)
             return False
 
+    def forget_plugin_fonts(self, plugin_id: str) -> bool:
+        """Drop the fonts ``plugin_id``'s manifest registered: its manifest
+        and catalog, its ``plugin_id::family`` entries in font_catalog, and
+        cached font objects for those families. Called by core when a plugin
+        is unloaded, so a reload registers from its current manifest and a
+        removed plugin's fonts stop resolving.
+
+        FontManager takes no locks; like forget_manager_fonts this relies on
+        single dict operations being atomic and iterates snapshots, so a
+        render thread calling get_font() meanwhile cannot break it. Returns
+        True if the plugin had registered fonts.
+        """
+        prefix = f"{plugin_id}::"
+        manifest = self.plugin_fonts.pop(plugin_id, None)
+        catalog = self.plugin_font_catalogs.pop(plugin_id, None)
+        # Every namespaced entry, not just the families in the catalog: one
+        # whose file failed to load never made it into the catalog, and a
+        # caller may have added one directly.
+        for family in list(self.font_catalog):
+            if family.startswith(prefix):
+                self.font_catalog.pop(family, None)
+        # get_font() keys the cache f"{family}_{size_px}".
+        dropped = [key for key in list(self.font_cache) if key.startswith(prefix)]
+        for key in dropped:
+            self.font_cache.pop(key, None)
+        if dropped:
+            # Font objects someone may hold were dropped; see cache_generation.
+            self.cache_generation += 1
+        if manifest is None and catalog is None:
+            return False
+        logger.info("Forgot fonts of plugin %s", plugin_id)
+        return True
+
     def _validate_font_manifest(self, font_manifest: Dict[str, Any]) -> bool:
         """Validate the structure of a plugin's font manifest."""
         required_fields = ["fonts"]