fix(workflow): reduce evolve cron from 3h to 6h

[verkyyi]

Summary

• Reduces evolve.yml cron schedule from every 3 hours (0 */3 * * *) to every 6 hours (0 */6 * * *)
• Cuts ~$34/week in pipeline costs (evolve alone is ~$69/week at current 3h frequency)
• No quality loss: last 40 consecutive runs produced 0 issues, 0% pattern yield

Test plan

• Astro build passes
• Verify evolve.yml triggers on 6h schedule after merge
• Monitor posture cycling still covers all 4 postures daily (4 runs/day at 6h interval)

Closes #154

🤖 Generated with Claude Code

[github-actions]

Coder agent: Updated fix (re-triggered run).

Changed files:

.commit-message
.github/workflows/evolve.yml
state/agent_log.md
state/project_state.md

[github-actions]

Reviewer agent: ✅ Reviewed and approved. Build passes, no hard blocks found.

Issue #154 Requirement Checklist:

• [DONE] evolve.yml cron changed from 0 */3 * * * to 0 */6 * * *
• [DONE] No other changes to the workflow file
• [DONE] PR opened with needs-review label (workflow YAML per autonomy rules)

Single-line cron change from 3h to 6h. Expected ~$34/wk savings at 0 pattern yield over 40+ consecutive runs. Easily reversible if research yield improves.