feat: add MCP tools for ingest pipeline control (status/pause/resume/retry-failed)

[Kinghammer1]

Summary

Adds 4 new MCP tools so AI agents can control the ingest pipeline without the UI, closing the gap described in the issue where ingest pause/resume was locked behind UI buttons.

New MCP Tools

Tool	Description
llm_wiki_ingest_status	Queue counts (pending/processing/failed/cancelled/completed), paused flag, and task list
llm_wiki_ingest_pause	Abort in-flight LLM task, stop new tasks from starting (token spend stops immediately)
llm_wiki_ingest_resume	Resume processing after pause
llm_wiki_ingest_retry_failed	Requeue all failed tasks back to pending

Architecture

The ingest queue lives entirely in frontend TypeScript (src/lib/ingest-queue.ts). Since the MCP server talks to the Rust HTTP API, a Tauri event bridge connects them:

1. Rust HTTP endpoints (api_server.rs): 4 new routes emit ingest-api://request Tauri events with a unique request ID
2. Frontend listener (ingest-api-bridge.ts): Listens for events, calls the corresponding ingest-queue function, responds via the ingest_api_response Tauri command
3. Rust response channel: The HTTP handler blocks on an mpsc channel until the frontend responds (15s timeout)

Changes

• src-tauri/src/api_server.rs: 4 new routes (/ingest/status, /ingest/pause, /ingest/resume, /ingest/retry-failed), event bridge with timeout, complete_ingest_api_request function
• src-tauri/src/lib.rs: ingest_api_response Tauri command + registration in invoke handler
• src/lib/ingest-api-bridge.ts (new): Frontend event listener that calls ingest-queue functions
• src/App.tsx: Start bridge on app startup
• mcp-server/src/api-client.ts: 4 new API client methods + types + parsers
• mcp-server/src/index.ts: 4 tool definitions + handler cases + output formatters
• mcp-server/test/api-client.test.ts: 4 new tests (all passing)

Testing

• MCP server: npm run typecheck and npm test — 24/24 tests pass
• Rust backend: cargo check — compiles cleanly
• Frontend TypeScript: npx tsc --noEmit — compiles cleanly

Backward Compatibility

• No changes to existing MCP tools or API endpoints
• No changes to the UI behavior — the ingest-queue functions are unchanged
• The new endpoints follow the same auth pattern as existing endpoints