Tasks: one work item may be delivered by several PRs (issue-101)

Phase 3 of 3. Derived from the locked design.md. TDD (tdd.mode: standard): the failing test comes first for every behavioural task.

DAG

flowchart LR
    T1[T1 failing dispatcher tests] --> T2[T2 _closing_refs]
    T2 --> T3[T3 handle close branch]
    T3 --> T4[T4 workspace tests]
    T3 --> T5[T5 webhook integration test]
    T3 --> T6[T6 poll regression test]
    T4 --> T7[T7 green gates]
    T5 --> T7
    T6 --> T7
    T7 --> T8[T8 templates + commands]
    T7 --> T9[T9 capability docs + decision]
    T8 --> T10[T10 PR + briefing]
    T9 --> T10

Tasks

• [x] T1 — Failing dispatcher unit tests (cli/tests/test_routing.py): a PR close leaves the linked issue's session active and delivers nothing; a PR close closes a session registered against the PR's own ref; a second PR closing ends nothing while the issue is open; the issue's own close still ends it. (AC1–AC5)
• [x] T2 — _closing_refs(routed) in cli/the_loop/webhook/dispatcher.py: pure, payload-only, issues → the issue's ref, pull_request → the PR's own ref, malformed payload → empty set. (AC1, AC4)
• [x] T3 — Close branch of Dispatcher.handle: skip a matched session whose ref is not in _closing_refs, logging it and emitting session.kept_open; everything else in the branch unchanged (never spawn, never prompt). (AC1, AC3, AC5)
• [x] T4 — Workspace tests: a PR close does not clean the work item's checkout; the closing PR's own session still does. (AC6, AC7)
• [x] T5 — Webhook integration test (test_webhook_routing_integration.py, Gherkin + Requirement: link): the work item's session survives its first PR merging, and the later issues closed webhook ends it. (AC1, AC2)
• [x] T6 — Poll-path regression test (test_poller_integration.py, Gherkin + Requirement: link): a merged PR vanishing from the listing while the issue is still listed closes nothing — guards findings C–E against regression. (AC1, AC2)
• [x] T7 — Green gates: make check from the repo root (ruff, ruff format, pyright, config validation, pytest) + markdownlint (hooks.prePush parity).
• [x] T8 — Templates & commands: execution-log.md template gains the Pull requests list; work-on.md / execute-tasks.md label and record every PR; finish-tasks.md verifies all of them before completing. (AC8, AC9)
• [x] T9 — Docs & decision: docs/capabilities/webhook-triggers.md (current behaviour + history row), docs/capabilities/spec-workflow.md (the PR list in the execution log), skills/the-loop/reference/automation.md, cli/README.md, and docs/decisions/decision-039.md + index. (AC10)
• [x] T10 — PR + reviewer briefing from skills/the-loop/templates/pr-briefing.md; phase label → loop:needs-review.