fix(web): correct 'disabled plugin' diagnosis for web backends (#59573)

When a bundled web provider (firecrawl, tavily, exa, ...) is listed in
plugins.disabled, its provider never registers and the web_search/
web_extract dispatchers emitted the misleading "No web extract provider
configured. Set web.extract_backend to ..." — even though the backend was
configured correctly. The real fix is to re-enable the plugin.

- web_tools.py + web_search_registry.py: when the configured backend names
  a disabled bundled web plugin, both dispatchers now point the user at the
  actual cause (re-enable the plugin) instead of a wrong config hint.
- plugins_cmd.py cmd_enable: enabling by canonical key now also clears the
  manifest-name alias (web-firecrawl) from plugins.disabled, so the
  suggested command actually re-enables the plugin ('explicit disable wins'
  matches on the name too).
- plugins_cmd.py cmd_toggle / _run_composite_ui / _run_composite_fallback:
  the interactive 'hermes plugins' menu now persists the canonical key
  (web/firecrawl), never the bare manifest name — the drift that put the
  offending entry in plugins.disabled in the first place.

Follow-up to #59518 (which fixed web credential resolution, a different
cause). Fixes the disabled-plugin symptom reported after that PR.

tools/web_tools.py

@@ -661,6 +661,7 @@ def web_search_tool(query: str, limit: int = 5) -> str:
         from agent.web_search_registry import (
             get_active_search_provider,
             get_provider as _wsp_get_provider,
+            _disabled_web_plugin_for,
         )
 
         backend = _get_search_backend()
@@ -672,13 +673,29 @@ def web_search_tool(query: str, limit: int = 5) -> str:
             provider = get_active_search_provider()
 
         if provider is None:
-            response_data = {
-                "success": False,
-                "error": (
-                    "No web search provider configured. "
-                    "Run `hermes tools` to set one up."
-                ),
-            }
+            # A bundled web plugin the user explicitly disabled looks
+            # identical to "no provider" here — point at the real cause
+            # (re-enable the plugin) rather than a generic setup hint.
+            disabled_key = _disabled_web_plugin_for(capability="search")
+            if disabled_key:
+                _vendor = disabled_key.split("/", 1)[-1]
+                response_data = {
+                    "success": False,
+                    "error": (
+                        f"web.search_backend is set to '{_vendor}', but its "
+                        f"plugin ('{disabled_key}') is disabled in config. "
+                        f"Re-enable it with `hermes plugins enable {disabled_key}` "
+                        "(or remove it from plugins.disabled)."
+                    ),
+                }
+            else:
+                response_data = {
+                    "success": False,
+                    "error": (
+                        "No web search provider configured. "
+                        "Run `hermes tools` to set one up."
+                    ),
+                }
         else:
             logger.info(
                 "Web search via %s: '%s' (limit: %d)",
@@ -814,6 +831,7 @@ async def web_extract_tool(
             from agent.web_search_registry import (
                 get_active_extract_provider,
                 get_provider as _wsp_get_provider,
+                _disabled_web_plugin_for,
             )
 
             provider = _wsp_get_provider(backend) if backend else None
@@ -839,6 +857,27 @@ async def web_extract_tool(
                     )
                 provider = get_active_extract_provider()
                 if provider is None:
+                    # If the configured backend is a bundled web plugin the
+                    # user explicitly disabled, the backend is set correctly
+                    # and the real fix is to re-enable the plugin — say so
+                    # instead of telling them to set web.extract_backend
+                    # (which they already did). #40190 follow-up.
+                    disabled_key = _disabled_web_plugin_for(capability="extract")
+                    if disabled_key:
+                        _vendor = disabled_key.split("/", 1)[-1]
+                        return json.dumps(
+                            {
+                                "success": False,
+                                "error": (
+                                    f"web.extract_backend is set to '{_vendor}', "
+                                    f"but its plugin ('{disabled_key}') is disabled "
+                                    "in config. Re-enable it with "
+                                    f"`hermes plugins enable {disabled_key}` "
+                                    "(or remove it from plugins.disabled)."
+                                ),
+                            },
+                            ensure_ascii=False,
+                        )
                     return json.dumps(
                         {
                             "success": False,