Skill instrumentation emits events that hooks now carry mechanically

[williamthorsen]

Problem

The instrumented skills emit lifecycle events whose information the harness hook channel now carries mechanically. input.received is starved in practice (28:6 under Claude, 5:0 under Rovo) while hook-emitted turn.started carries the same signal reliably, and skill.progress duplicates turn.* recency in the lane-view fold. The redundant emits cost tokens on every instrumented run and widen the agent-compliance surface for no fleet-view gain.

Context

The #985 findings ratify a two-channel design: hooks carry the session lifecycle (session.*, turn.*); skills emit only what hooks cannot know — work semantics. The slimmed per-skill set is skill.started, skill.completed, artifact.written/pr.created where applicable, and input.requested with its ask payload.

Proposed solution

Retire input.received from the declared vocabulary and remove its emits; remove skill.progress emit instructions from the four instrumented skills (create-pr, implement-plan, respond-to-review, review-branch) while keeping the type declared as optional step-level detail; slim the emit-event skill's vocabulary reference to match; and drop the input.received case from the fleet-view lane-view fold, where the resume state already derives from the relayed turn.started.

Acceptance criteria

Must have

• Instrumented skills emit only the slimmed set: skill.started, skill.completed, artifact.written/pr.created where applicable, and input.requested.
• input.received is removed from the declared vocabulary and no skill emits it.
• The lane view derives waiting and resume states from hook events with no regression in derived status.