agent communication via append-only md files

[crrow]

Context

CEO/BOSS/sub-agent communication currently overwrites JSON.
Should use append-only markdown log files instead.

Design

• goal/log/cycle-NNN-ceo.md per CEO cycle
• goal/log/cycle-NNN-boss.md per BOSS review
• Never modify existing files, only create new ones

Acceptance

• Remove .boss-review.json overwrite pattern
• BOSS daemon writes new md per review
• CEO reads latest BOSS md before next cycle