Tasks: dispatch-lifecycle emoji reactions

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

• [x] T1 — ReactionConfig + palette. New cli/the_loop/reactions.py: REACTION_CONTENTS (REST↔GraphQL names), state constants, ReactionConfig (from_mapping, content_for; enabled default False). (AC2.1–2.3)
• [x] T2 — target_from_event. Pure target resolution per design §1 (provider guard, owner/repo + id validation, comment REST/GraphQL split, issue/PR fallback, None for the rest). (AC1.4, AC3.1, AC3.2) — depends on T1.
• [x] T3 — GitHubReactor. react(routed, state) with the short-circuit ladder, gh api REST/GraphQL invocation via injectable runner, warn-once on missing gh, reaction.added/reaction.failed emission, never raises. (AC1.1–1.3, AC1.5, AC3.3, AC4) — depends on T2.
• [x] T4 — Dispatcher wiring. RoutingConfig.reactions; optional reactor ctor param (+ override survives reload); _worker reacts started/completed/error; _dispatch_one/_spawn_for/_spawn_tmux/ _respawn_tmux return bool. (AC1.1–1.3, AC1.6, AC2.4) — depends on T3.
• [x] T5 — Event-log types. Register reaction.added / reaction.failed in eventlog.EVENT_TYPES. (AC4) — depends on nothing.
• [x] T6 — Config schema + example. routing.reactions in .the-loop/cli-config.schema.json (enum-guarded states, defaults) and the dogfood block (enabled: true) in .the-loop/cli-config.yaml; make validate green. (AC2.1–2.3) — depends on T1.
• [x] T7 — Unit tests. cli/tests/test_reactions.py per design testing strategy. — depends on T1–T3.
• [x] T8 — Integration tests. Dispatcher-level reaction scenarios with a recording fake reactor + Gherkin docstrings. — depends on T4.
• [x] T9 — Docs. cli/README.md reactions section; docs/capabilities/webhook-triggers.md behaviour + history row. (The observability reference needs no edit: its catalog's source of truth is EVENT_TYPES, kept in sync by a unit test.) — depends on T4.
• [x] T10 — Gates. make check (ruff, markdownlint, format, pyright, validate, pytest) fully green; evidence in execution-log.md. — depends on T1–T9.