fix: preserve ignored state during blocked retry

[rochecompaan]

Summary

• classify ordinary worktree cleanliness and ignored inventory independently
• preserve all ignored state for verified in-place blocked-run resumes and report that preservation before Pi starts
• keep refresh, recreation, and reset fail-closed, including late ignored-content races and missing-worktree unique-commit reset protection
• document the path-agnostic preservation and destructive-refusal policy

Validation

• focused recovery/pipeline/mutation/reset tests: 58 passed
• npm run test:run-once: 575 passed
• npm test: 1,532 passed
• npm run lint
• npm run build
• npm run site:build
• git diff --check
• dependency metadata unchanged; Nix build not required

Reviews

• Final Codex full-worktree review passed after accepted test and reset-safety fixes.
• Final thermo-nuclear full-worktree review passed after focused policy-structure fixes.
• Final validation-readiness review passed against fresh exact-HEAD logs.

Closes #211

Patchmill run cost

Stage	Model	Prompt tokens	Output tokens	Estimated cost (USD)
Planning	gpt-5.6-sol	3,571,786	28,419	$3.3231
Development environment	gpt-5.6-sol	327,899	2,666	$0.5450
Implementation	gpt-5.6-sol	17,590,288	126,071	$19.1516
Implementation	gpt-5.6-terra	11,091,074	35,443	$3.7681
Implementation subtotal		28,681,362	161,514	$22.9198
Total		32,581,047	192,599	$26.7879

Prompt tokens include uncached input, cache reads, and cache writes. Cost is an estimate based on Pi's recorded model pricing and includes parent and subagent sessions.