feat(kb): Matrix chat transcript → KB claims extraction pipeline

[mdheller]

Summary

• Adds turtle-transcript-extract binary: fetches Matrix room history, groups messages into substantive threads, distills each via turtle-noetica-stream, writes KB claims to ~/.local/state/sourceos/transcript-claims/pending.jsonl, and commits them as YAML to systems-learning-loops/kb/claims/
• Adds txextract, txcommit, txlist shell functions to turtle-shell-init.zsh
• Adds three palette entries (📜 Transcript) to turtleterm.lua with matching dispatch actions

Claim format

Committed claims are YAML with id, extracted_at, source, room_id, thread_event_ids, tags, claim, confidence, evidence_summary.

Thread detection heuristics

A thread is substantive if: ≥3 messages, or question (?) + reply, or !qes operator command + reply, or ≥2 messages with any body >100 chars.

Test plan

• python3 -m py_compile assets/sourceos/bin/turtle-transcript-extract — passes
• turtle-transcript-extract status — shows config/token/pending state
• turtle-transcript-extract extract --dry-run — extracts without writing
• txextract --since 1 in TurtleTerm shell — invokes binary via shell alias
• Palette CMD+P → search "transcript" → entries appear, SendString fires correctly