AI Document Summary

Adds a Summary sidebar panel and a Summarize context-menu action for supported
document types (PDF, TXT, MD). On demand it downloads the file, extracts its
text, and sends it to an admin-configured, OpenAI-compatible LLM endpoint to
produce a short overview and a list of key points.

No LLM provider is bundled and no API keys are embedded in the browser — the
endpoint is fully operator-controlled (BYO-LLM). Requests flow through an
ai-llm-proxy sidecar that validates the user's oCIS bearer token and injects
the LLM API key server-side so it never reaches the browser.