feat(extensions): add OAuth setup UI for WASM tools + display name labels (#437)

Add setup.required_secrets to tool capabilities.json files so users can
configure OAuth client credentials (Google, Slack, Okta, Telegram) through
the Extensions UI Setup modal instead of environment variables.

- Add ToolSetupSchema/ToolSecretSetupSchema types to capabilities_schema.rs
- Extend get_setup_schema(), save_setup_secrets(), list() to handle WasmTool
- Extract load_tool_capabilities() helper to reduce duplication
- Auto-activate tools after saving setup secrets
- Show display_name labels (Channel/Tool/MCP) in extension cards
- Update button labels: "Setup" when unconfigured, "Reconfigure" when set
- Replace "Set" badge with checkmark in configure modal
- Fix innerHTML XSS pattern in slash autocomplete (use textContent)
- Add tests for ToolSetupSchema parsing and resolve_nested promotion
- Update registry display names (e.g. "Telegram Channel" vs "Telegram Tool")

Co-authored-by: Claude Sonnet 4.6 <[email protected]>

tools-src/google-sheets/google-sheets-tool.capabilities.json

@@ -41,5 +41,17 @@
       }
     },
     "env_var": "GOOGLE_OAUTH_TOKEN"
+  },
+  "setup": {
+    "required_secrets": [
+      {
+        "name": "google_oauth_client_id",
+        "prompt": "Google OAuth Client ID (from console.cloud.google.com/apis/credentials)"
+      },
+      {
+        "name": "google_oauth_client_secret",
+        "prompt": "Google OAuth Client Secret"
+      }
+    ]
   }
 }