docs: make G3 scratch ratchet negative

[briansrls]

Summary

• Follow-up to docs: add G3 coercion-fold scratch retirement brief #1878 review feedback after merge.
• Changes the G3 scratch-retirement verification command from positive rg to negative ! rg, so the command succeeds only when retired scratch identifiers are absent.

Verification

• git diff --check

[briansrls]

Review metadata

• Provider / model: codex / codex-default
• Commit: 87764044 · Trigger: schedule
• Comparison: origin/main @ 831080de ... review/pr-1894-87764044 @ 87764044
• Thinking: 25s wall

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Verdict: APPROVE. Diff is a narrow docs-only fix that turns the ratchet command into a negative assertion (! rg ...) in docs/briefs/r3-grounding-g3-coercion-fold-scratch-retirement-worker.md. That aligns the verification step with the stated intent of proving those identifiers are gone; I don’t see any violation of the pinned invariants, modeling, coding, or testing guidance in this diff.

[briansrls]

Review metadata

• Provider / model: codex / unknown
• Commit: 87764044 · Trigger: schedule
• Thinking: 74s wall

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Non-blocking — Strengths

• docs/briefs/r3-grounding-g3-coercion-fold-scratch-retirement-worker.md The negative rg ratchet aligns verification with the acceptance requirement that scratch selectors have no surviving code references.

✅ No blocking concerns; this is a clean docs-only correction to the G3 scratch-retirement verification command.