refactor(acm): dao-shu guidance reshape (Composer proposal)

[KorenKrita]

Summary

Composer-proposed reshape of always-on ACM guidance from mechanical Required transition rules toward 道术 separation: principles the model can reason from, with runtime enforcement kept at the tool layer.

• 道: causal opening (working set grows → boundary → handoff), Decision smells, Failure shapes, and fold-gate self-check before travel
• 术 (soft): Recognizable moments table — observables → what becomes reasonable, not mandatory
• 术 (hard): mixed tool-batch rejection stays in runtime; CORE only notes that validation exists
• Preflight reframed as managed-chain completion (<chain>-start recoverability confirmed) instead of "first action must be checkpoint"
• GUIDANCE_CUES re-anchored with positive targets (e.g. handoff snapshot sourcing, cold-start test for root)
• SKILL router updated to point advanced cases at gates-passed-but-ambiguous decisions

Design intent

Inspired by writing-great-skills: fewer negations, stronger leading words, checkable completion criteria (fold gate), progressive disclosure to context-management skill for archive/exception paths.

Test plan

• bun run verify:acm (guidance check, 87 root tests, typecheck, host fixture)
• Guidance quality tests lock smells/gates/managed-chain preflight contracts
• Tool description and rebase-evidence tests still pass

Worktree

Branch developed in worktree at ../pi-context-composer-guidance.

[KorenKrita]

Superseded by #12 (chosen merge target for ACM dao-shu guidance). Closing this alternative.