refactor: close src/utils retirement and enforce no-regrowth

[thymikee]

Parent: #2129

Blocked by: #2133, #2134, #2135, #2136, #2138, #2139, #2140, #2141, #2142, #2143, #2144, #2145, #2146, #2147, and #2148. Final wave only: every owner slice must be merged/reviewable before terminal cleanup.

Scope — exact terminal files

Update the existing enforcement/metadata files:

• scripts/layering/model.ts
• scripts/layering/model.test.ts
• scripts/layering/check.ts
• scripts/layering/check-wiring.test.ts
• scripts/mutation/modules.ts
• scripts/mutation/config.test.ts
• scripts/mutation/selection.test.ts
• scripts/mutation/ownership.test.ts only if the moved source/test topology changes its derived assertion
• scripts/__tests__/test-file-size-ratchet.test.ts
• stryker.config.json
• fallow-baselines/health.json
• src/__tests__/eager-closure-budgets.ts
• packages/kernel/src/device.ts
• packages/selectors/src/internal/parse.ts

Add the structural retirement rule and its tests:

• scripts/layering/src-utils-retirement.ts
• scripts/layering/src-utils-retirement.test.ts

The update child owns tsdown.config.ts and src/__tests__/update-check.test.ts; the surface child owns active output/help-conformance imports. Coordinate those edits rather than duplicating them here.

Required terminal changes

1. Prove the final tracked tree with git ls-files 'src/utils/**' and fail by rule name if any tracked utility path remains, including a test or fixture. The new rule must be wired into LAYERING_RULE_IDS and LAYERING_RULES, report an actionable path, and have a synthetic planted-red test that fails on src/utils/regrown.ts before the final green run.
2. Remove utils from TARGET_DAG_RANK; update the model assertion/comment so the old zone is not silently classified. Keep all remaining production zones deliberately ranked or unranked.
3. Point the mutation registry/config/selection fixtures at the final src/snapshot/scroll-edge-state.ts owner and preserve derived ownership through src/commands/interaction/runtime/gestures.test.ts. Do not leave a Stryker glob or affected-selection fixture at the deleted path.
4. Move/remove exact test-size pins after the output and daemon-client test relocations. A pin must follow a file only when that file still exists and remains over the tripwire; a split output test must not be pinned.
5. Remove only stale fallow baseline keys for deleted utility paths, moving a key only when the same finding belongs to the exact destination. Do not bulk-regenerate or accept unrelated findings.
6. Re-audit every remaining src/utils string. Keep deliberate synthetic fixture paths in depgraph/package-boundary tests only when the test is explicitly testing arbitrary path parsing; update stale production/comments/packaging references. The final report must distinguish retained test fixtures from stale metadata.

Behavior invariants

The terminal wave changes no command behavior, snapshot presentation policy, app-log/transport/provisioning/Swift/video policy, wire shape, errors, timeouts, retries, or lazy loading. It only closes the deletion invariant and keeps layering/mutation/test-size/fallow metadata truthful.

Focused and final validation

Run the new retirement test against the planted src/utils/regrown.ts fixture and record the named red result, then remove the fixture. Run:

• pnpm vitest run scripts/layering/src-utils-retirement.test.ts scripts/layering/model.test.ts scripts/layering/check-wiring.test.ts
• pnpm vitest run scripts/mutation/config.test.ts scripts/mutation/selection.test.ts scripts/mutation/ownership.test.ts
• pnpm vitest run scripts/__tests__/test-file-size-ratchet.test.ts
• pnpm check:affected --run
• git ls-files 'src/utils/**' (must be empty)
• the full affected check again after staging any new structural rule so the tracked-file layering scanner sees it

Planted-red proof

This child adds the no-regrowth rule. Before wiring the rule, add a temporary tracked fixture path src/utils/regrown.ts to the synthetic input and observe a failure containing the rule name R14 src-utils-retirement and the path. Then wire the rule, run the same planted-red test, remove the fixture, and record the final green result. Do not allowlist a path or use a filename-only heuristic.

Dependency order

No terminal cleanup is ready until every parent child has a complete owner decision and its old src/utils paths are gone. This child is the final closure/no-regrowth proof and must not be merged ahead of any owner move.

Shrink target

Final invariant: git ls-files 'src/utils/**' returns no paths; no old utility zone is ranked; no stale packaging, mutation, size-ratchet, or fallow metadata claims ownership of it; and the no-regrowth rule fails by name on a planted path. The terminal diff must delete metadata rather than replace it with a new shared registry, and the full program must have net production shrinkage after discounting physical moves.