v0.8.1 — YouTube playlists, plain text, fail summary, and docs

Patch release: YouTube playlist indexing, plain text file indexing, MCP async and logging improvements, fail summary by reason, and documentation updates.

Features

• YouTube playlist indexing — Index all videos in a playlist via `add_document_tool` (yt-dlp for video IDs; transcript proxy config in .env).
• Plain text indexing — Index plain .txt files (non-Discord); configurable file-size cap via `PINRAG_PLAINTEXT_MAX_FILE_BYTES`.
• Fail summary by reason — `add_document_tool` returns `fail_summary` with counts: `blocked`, `disabled`, `missing_transcript`, `other` (e.g. YouTube IP blocking vs transcripts disabled).

MCP server

• Async tools and resources — MCP tools and resources run via `anyio.to_thread.run_sync` so indexing does not block the event loop.
• Logging — PinRAG logs disabled by default to avoid Cursor stderr "undefined" spam; set `PINRAG_LOG_TO_STDERR=true` for debugging. Tool completion timing logged when enabled.

Configuration

• YouTube proxy — `PINRAG_YT_PROXY_HTTP_URL` and `PINRAG_YT_PROXY_HTTPS_URL` for transcript fetches when YouTube blocks your IP (see README).

Documentation

• README — YouTube IP blocking and proxy workaround, residential proxy note, Monitoring & Observability (LangSmith), proxy env vars in config table.
• Implementation checklist — Deployment (PyPI), backup, metrics/logging, docs, QoL and Phase 6 updates; MMR analysis in `notes/mmr-analysis.md`.
• AGENTS.md — Added for Cursor/agent use.