feat: executor-narrative channel — tdd note command and friction-log rendering (issue #77)

[geuben]

Summary

• Adds tdd note "<text>" — a free-text executor-narrative command scoped to the open cycle and phase, or to the run after it ends
• Adds schema v8: a new note table (run_id, cycle_id, phase, text, at) with MIGRATIONS[7] = "" entry
• Renders cycle notes as blockquotes inside their cycle section of the friction log; run-level notes in a new ## Executor narrative section between cycles and Blockers
• Soft nudge on _reply envelopes when integrity events exist and the cycle has no note yet; silenced once a note is recorded
• Closing-narrative invitation on both terminal COMPLETE envelopes (_handle_refactor and cmd_cycle_skip's final-cycle path)
• Docs follow-up: README command table + friction-log section, PRD Note entity + command table + schema v8, harness-integration, tdd-drive SKILL.md

Commits

afbfeaf docs: add tdd note to README, PRD, harness-integration, and tdd-drive skill
cc3b871 docs: friction log for issue-77-executor-notes
c5d9115 feat: closing-narrative prompt on the terminal skip envelope
26df7d8 test: COMPLETE via final-cycle skip mentions the closing tdd note
c46a2f8 feat: closing-narrative prompt on the terminal advance envelope
35eb703 test: COMPLETE via advance mentions the closing tdd note
cfebfe0 feat: silence the note nudge once the cycle carries a note
5eb02ff test: a noted cycle is not nudged again
558cfe2 refactor: an integrity event's envelope nudges for a note
abaae1a feat: soft note nudge on integrity-event envelopes
08a02ac test: red_first_violation envelope suggests tdd note
dcf0558 refactor: no Executor narrative section without run-level notes
4d05f83 feat: Executor narrative section for run-level notes
fff34b9 test: run-level notes render under ## Executor narrative
5760d71 feat: friction log renders cycle notes as blockquote claims
3c20256 test: a cycle note renders as a phase-stamped blockquote
887b568 feat: tdd note falls back to the latest run after the run ends
19dc0f5 test: post-terminal tdd note lands run-level, no active run required
96a00b1 refactor: a v7 ledger is upgraded in place to v8
b8d48c2 feat: schema v8 — note table, empty MIGRATIONS[7] entry
5409f1b test: reopening a v7 ledger yields the note table and version 8
3478582 feat: tdd note — executor-narrative rows in a new note table
3d6cb70 test: tdd note stores a cycle-scoped, phase-stamped row

Quality gates

• uv run ruff check src tests — All checks passed
• uv run pytest tests/ — 461 passed

Test coverage note

All decision-point operators in new code are covered by at least one test (pseudo-mutation analysis passed). 10 cycles, 10 tests in tests/test_executor_notes.py. Cycle 6 passed on arrival as predicted by the plan; sensitivity check confirmed it can fail under mutation.

Closes #77