feat: label and narrate the delegation state notices

[cgaravitoq]

A deployment that sets progress.narration reads Spanish in every thread, but the delegation state notices stayed English: packages/core/src/delegation.ts built them from a hardcoded map and posted them itself, so no config could change them and no narration turn ever saw them.

delegation.labels now names the word each notice opens with (running, failed, unknown), missing or blank values keep today's English strings, and a configured narration hands the labelled notice to the same narration path a milestone takes, keyed delegation:<task id>:<state>, with the labelled line as that turn's fallback. Without narration the notice is posted directly as before.

Verify:

• A config with Spanish labels posts "Iniciado." on running in the no-narration deployment: a Spanish deployment posts its labelled notice directly, once per state in apps/slack-agent/test/delegation.test.ts posts ["Iniciado.", "Desconocido. Budget ended ", "Fallido. Stop confirmed"] for running, unknown and failed.
• With narration configured the running notice reaches the narration path with the label and the note, and nothing is posted directly: a narrated deployment hands the labelled notice to the narration turn and posts nothing itself records one notice (conductor: "runner-1", label: "Iniciado", note: "Budget ended ", state: "running"), builds its turn with delegationNoticeTurn, asserts idempotencyKey === "delegation:task-1:running", binding.fallbackText === "Iniciado. Budget ended ", the shared instruction and Status: Iniciado in the body, and that h.posts grew by zero.
• A repeated running still posts nothing: the same test reports running twice and expects one line; a repeated runner state answers 200 once and another runner is still refused still expects ["Started.", "Failed."] for two running and two failed reports.
• Labels absent means today's strings: delegation without labels keeps today's English notice posts ["Started.", "Outcome unknown. Budget ended", "Failed. Stop confirmed"], and delegation labels resolve from config and fall back when blank or absent asserts a blank failed resolves to Failed through defineAgentConfig.
• On base f28de36 these tests cannot pass: a detached worktree at f28de36 with only the new test file copied in fails to load it with SyntaxError: Export named 'delegationNoticeTurn' not found in module 'packages/core/src/index.ts', and bun -e against base's defineAgentConfig with delegation.labels = { running: "Iniciado" } prints labels on base: undefined.
• bun run verify is green: 376 pass, 0 fail, plus knip, deploy:dry and bun audit clean.

Commits, in dependency order:

1. test: demand Spanish delegation notices and their narrated turn
2. feat: label and narrate the delegation state notices
3. docs: document the delegation notice labels and their narration

Notes:

• SlackProgressTurn.milestoneId became idempotencyKey, so the host dispatches under the key the turn carries: progress:<milestone id> for milestones, delegation:<task id>:<state> for notices. apps/slack-agent/test/progress.test.ts and apps/slack-agent/test/worker-stream.test.ts build or compare a turn literal and moved with it.
• apps/slack-agent/src/index.ts wires the notice narrator because that is where narrateProgressTurn and trusted.teamId live; apps/slack-agent/src/delegation.ts only forwards the optional callback.

Not covered: right-hand's Spanish values (row R1) and the live thread (wave-end pass).