Tasks: bounded per-event retry policy + respawn dead tmux sessions

Phase 3 of 3 (bugfix → design → tasks). DAG — a task starts once its dependencies are checked.

• [x] T1 — TmuxResult.session_missing. Add session_missing: bool = False to TmuxResult; set it True on TmuxRunner.deliver's has_session-false early return. (AC7, AC8)
• [x] T2 — Dispatcher.delivery_status. Add delivery_status(delivery_id, refs) -> "done"|"inflight"|"unhandled" reading recent_deliveries (done), the dedup cache (inflight), else unhandled. (AC2, AC5) — depends on nothing.
• [x] T3 — Respawn on delivery. In _dispatch_one, when the tmux delivery fails and result.session_missing, call new _respawn_tmux(session, routed, prompt): reuse session.harness/cwd/tmux_target, mint a new id, tmux.spawn with the event prompt as boot prompt, re-register (force=True, preserving recent_deliveries), touch, emit session.respawned; fail-closed + release on any inability. (AC7, AC9) — depends on T1.
• [x] T4 — polling.maxRetries config. Add to .the-loop/cli-config.schema.json (integer, default 3, min 1) and .the-loop/cli-config.yaml; mirror on PollConfig (from_mapping) and add a --max-retries flag to poll start. (AC1)
• [x] T5 — PollState retry ledger. Replace the flat baseline with seenComments (resolved) + commentAttempts + spawn ({attempts, gaveUp, deliveryId}); add accessors and finalize(ref, live_ids, polled_at) pruning both maps to the live thread. Round-trips through the JSON file. (AC2–AC6)
• [x] T6 — _process_item retry flow. Rewrite to: baseline dropped (unauthorized/self) comments; arm/retry the spawn with the budget (_try_spawn, armed by first sight / new activity / in-progress, re-armed by a new comment); process each unresolved candidate comment via delivery_status (done→resolve, inflight→wait, unhandled→retry/give-up); finalize at cycle end. Emit poll.spawn_failed/poll.comment_failed on give-up and add attempt to poll.comment_forwarded. Add failures to PollSummary/poll.cycle. (AC2–AC6) — depends on T2, T4, T5.
• [x] T7 — Event types. Register session.respawned, poll.spawn_failed, poll.comment_failed in EVENT_TYPES; note attempt on poll.comment_forwarded. (AC10) — depends on T3, T6.
• [x] T8 — Tests. Unit: session_missing (T1), delivery_status (T2), PollState ledger (T5). Integration: respawn-on-dead-session + no-respawn on other failure (test_tmux_runner_integration.py); comment retry→give-up→ ignore, new-comment-retriggers, success-baselines (test_poller_integration.py / test_poller.py) — Gherkin docstrings + requirement links. (all AC) — depends on T1–T7.
• [x] T9 — Capability docs. Update docs/capabilities/interactive-sessions.md (respawn) and docs/capabilities/webhook-triggers.md / the poller capability doc (retry policy) with current behaviour + history rows.
• [x] T10 — Gates. ruff check / ruff format --check, pyright, pytest all green; update execution-log.md.