fix: auto-repair missing plugins and graceful config fallback

Plugins whose directories are missing (failed update, migration, etc.)
now get automatically reinstalled from the store on startup. The config
endpoint no longer returns a hard 500 when a schema is unavailable —
it falls back to conservative key-name-based masking so the settings
page stays functional.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web_interface/blueprints/api_v3.py

@@ -33,6 +33,23 @@ from src.web_interface.secret_helpers import (
     separate_secrets,
 )
 
+import re
+
+_SECRET_KEY_PATTERN = re.compile(
+    r'(api_key|api_secret|password|secret|token|auth_key|credential)',
+    re.IGNORECASE,
+)
+
+def _conservative_mask_config(config):
+    """Mask string values whose keys look like secrets (no schema available)."""
+    result = dict(config)
+    for key, value in result.items():
+        if isinstance(value, dict):
+            result[key] = _conservative_mask_config(value)
+        elif isinstance(value, str) and value and _SECRET_KEY_PATTERN.search(key):
+            result[key] = ''
+    return result
+
 # Will be initialized when blueprint is registered
 config_manager = None
 plugin_manager = None
@@ -2505,24 +2522,14 @@ def get_plugin_config():
             }
 
         # Mask secret fields before returning to prevent exposing API keys
-        # Fail closed — if schema unavailable, refuse to return unmasked config
         schema_mgr = api_v3.schema_manager
-        if not schema_mgr:
-            return error_response(
-                ErrorCode.CONFIG_LOAD_FAILED,
-                f"Cannot safely return config for {plugin_id}: schema manager unavailable",
-                status_code=500
-            )
+        schema_for_mask = schema_mgr.load_schema(plugin_id, use_cache=True) if schema_mgr else None
 
-        schema_for_mask = schema_mgr.load_schema(plugin_id, use_cache=True)
-        if not schema_for_mask or 'properties' not in schema_for_mask:
-            return error_response(
-                ErrorCode.CONFIG_LOAD_FAILED,
-                f"Cannot safely return config for {plugin_id}: schema unavailable for secret masking",
-                status_code=500
-            )
-
-        plugin_config = mask_secret_fields(plugin_config, schema_for_mask['properties'])
+        if schema_for_mask and 'properties' in schema_for_mask:
+            plugin_config = mask_secret_fields(plugin_config, schema_for_mask['properties'])
+        else:
+            logger.warning("[PluginConfig] Schema unavailable for %s, applying conservative masking", plugin_id)
+            plugin_config = _conservative_mask_config(plugin_config)
 
         return success_response(data=plugin_config)
     except Exception as e: