feat: add web search, file edit, MCP management, file refs, and /stop to CLI/TUI
1. Web search tools (multi-provider): web_search, web_search_news, web_search_providers
- Brave, Tavily, SearXNG (env-var activated), DuckDuckGo (always available)
- Auto mode tries providers in priority order
2. File edit tool (fs_edit_file): targeted text replacement with validation
- Unique oldText matching, overlap detection, atomic application
- Sandboxed with size limits
3. MCP management commands: /mcp status, /mcp servers, /mcp reconnect <name>
- Shows connection status, tool counts, errors for all MCP servers
- Reconnect disconnected servers from the TUI
4. File reference in chat: @path/to/file inline expansion + /attach command
- Auto-detects @file patterns and inlines contents as fenced code blocks
- 256KB per file limit, max 10 files per message
- Language-aware syntax highlighting hints
5. /stop command: abort streaming via Pi SDK abort()
- New AbortPayload type in @mosaic/types
- Gateway abort handler calls piSession.abort()
- TUI emits abort event on /stop
fcb792a65d