feat(quality-depth): add build depth & documentation guidance

[MacAttak]

Summary

• Add post-build code review with heuristic trigger (4+ tasks, 5+ files, security-tagged) to sw-build
• Add as-built notes guidance (plan deviations to plan.md, spec untouched) to sw-build
• Update DESIGN.md token target from 600 to 800, replace estimated protocol tokens with actual measured values
• Resolve AUD-008 and AUD-009 in AUDIT.md

Acceptance Criteria

#	Criterion	Status
AC-1	Post-build review guidance exists in sw-build	PASS
AC-2	As-built notes guidance exists in sw-build	PASS
AC-3	DESIGN.md token target updated	PASS
AC-4	AUD-008 and AUD-009 resolved in AUDIT.md	PASS
AC-5	sw-build token budget managed	PASS

Gate Results

Gate	Status	Findings (B/W/I)
gate-build	SKIP	Markdown-only unit
gate-tests	SKIP	Markdown-only unit
gate-security	SKIP	Markdown-only unit
gate-wiring	SKIP	Markdown-only unit
gate-spec	PASS	0/0/0

Evidence

• Spec compliance: .specwright/work/quality-depth/units/build-depth-docs/evidence/spec-compliance.md
• Protocol extraction used to manage sw-build token budget (1,135 words with protocols/build-quality.md for detail)

Work unit: quality-depth/build-depth-docs (Unit 3 of 3 — final unit)