fix: office-hours marks sessions "success" without writing design doc

[walton-chris]

Summary

The office-hours skill can log outcome:success in the timeline even
when Phase 5 (design doc write) was skipped. The session looks
complete in telemetry, but no *-design-*.md artifact exists on disk,
silently breaking downstream skills (/plan-ceo-review,
/plan-eng-review) that read design docs from
~/.gstack/projects/{slug}/.

Repro

Observed in the wild on an apex-coach session (2026-04-12):

{"skill":"office-hours","event":"completed","branch":"master",
 "outcome":"success","duration_s":"0","session":"unknown",
 "ts":"2026-04-12T11:59:40.368Z"}

duration_s:"0" and session:"unknown" are a separate shell-state bug
addressed in a companion PR. But the real issue here is
outcome:"success" logged against ~/.gstack/projects/apex-coach/
which contains zero *-design-*.md files. A session with no
persisted artifact is not a successful session.

Fix

Two changes to office-hours/SKILL.md.tmpl:

1. New section "Pre-Telemetry: Verify Design Doc Artifact" inserted
   before the {{LEARNINGS_LOG}} placeholder. It re-derives SLUG,
   uses the preamble's ~/.gstack/sessions/\$PPID touch file as a
   session-start time reference, and finds any *-design-*.md
   written after that time. Emits ARTIFACT_STATUS: ok or no_doc.

2. New rule in Important Rules instructing Claude to use the
   artifact check to drive OUTCOME in the preamble's telemetry
   block. Log outcome:no_doc when no doc was written, never
   outcome:success.

Net diff: +56 lines, 0 deletions. Zero impact on sessions that
correctly write a doc.

Test plan

• Run `/office-hours` on a new project, complete Phase 5, confirm
  timeline logs `outcome:success` and artifact exists
• Run `/office-hours`, abandon mid-conversation, confirm timeline
  logs `outcome:no_doc`
• Run `/office-hours` in a project with existing old design docs,
  confirm the `-newer` check correctly distinguishes this session's
  doc from prior ones

Generated with Claude Code