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]>

registry/tools/slack.json

@@ -1,9 +1,9 @@
 {
   "name": "slack-tool",
-  "display_name": "Slack",
+  "display_name": "Slack Tool",
   "kind": "tool",
   "version": "0.1.0",
-  "description": "Post messages, read channels, and manage conversations via Slack API",
+  "description": "Your agent uses Slack to post and read messages in your workspace",
   "keywords": ["messaging", "chat", "workspace"],
 
   "source": {