Tasks: the clause reader stops at the phases; the close path waits for the endgame

Phase 4 of 4. Each task names the requirement it satisfies and the testing-plan row that proves it; the test lands with the change (red first).

Task list

[x] A1 — strip_signature and the clause cleaning. verbs.strip_signature; without_clause strips the signature, Cf characters and *_~ wrappers. Req: R1.1, R1.2 · Test: T1.
[x] A2 — apply_without reasons and the position-naming refusal. 3-tuple return, UNKNOWN_PHASE / UNSKIPPABLE_PHASE / EMPTY_CLAUSE; the non-token refusal; the three existing call sites updated. Req: R1.3, R1.4 · Test: T1, T9. Deps: A1.
[x] A3 — the pipeline logs and records what it read. _selection_grammar passes the reason, logs the text, _read_summary on the drop; the channel.dropped catalogue. Req: R1.4, R1.5 · Test: T2, T9. Deps: A2.
[x] B1 — the graph context knows the endgame. GraphContext.terminal, .delivered_by_merge; _context_from fills them. Req: R2.1, R2.5 · Test: T5.
[x] B2 — finishGraceSeconds. TmuxConfig.finish_grace_seconds, both schema copies, routing-options.md. Req: R2.2, R2.3 · Test: T4.
[x] B3 — the deferred closure. _PendingClose, _defer_close, _close_ended_session, sweep_closing, is_closing, _cancel_close, the sweeper thread, stop(); the close branch and _record_reopen wired; the merged flag; the poller skip; the event catalogue. Req: R2.1–R2.5 · Test: T3, T9. Deps: B1, B2.
[x] B4 — the session's endgame order. commands/finish-tasks.md, SKILL.md. Req: R2.6. Deps: B3.
[x] C1 — docs, reports and evidence. The run-3 report and the e2e series in docs/reports/index.md; followups/ P1/P2 notes and README rows; capability docs (channels.md, interactive-sessions.md, webhook-triggers.md) with history rows; evidence files; the testing plan completed. Deps: A3, B4.

Dependency graph (DAG)

Checkpoints

After A1–A3: tests/test_channels_verbs.py, tests/test_selection_control.py green.
After B1–B3: tests/test_finish_grace.py, tests/test_graph_drive.py, tests/test_schema_parity.py, tests/test_routing.py green.
After C1: full suite, ruff, ruff format, pyright, markdownlint, validate_config.

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