Quote revisions in Dev Brain test fixtures

docs/issue115-revision-fixture/README.md

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+# Issue 115: quoted Git revisions in the Dev Brain fixture
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+The test fixture now serializes the abbreviated Git revision with `serde_json::to_string`, whose quoted string is valid YAML. Both the real Git test and the deterministic parser regression use this same fixture builder. No production schema or source-version behavior changed.
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+The parser regression covers `9839678` (the reported decimal failure), `0000001` (leading zeros), `5568e06` (scientific notation, also observed during #114), and `abcdef0`. It uses the production Markdown frontmatter parser and deserializes the production `TopicFrontmatter`, asserting the exact original string.
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+Review against the issue confirms the existing real Git controls remain: seven-character minimum revision, source-specific history, unrelated dirty/committed file, unchanged fingerprint, modified actual source, committed actual source drift, and hash-backed dirty-source knowledge. No retries or weakened assertions were introduced. Dev Brain is DS4Server functionality; neither the pinned DS4 nor MTPLX has a corresponding feature or fixture. Model execution and token processing are untouched.
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+Verification on 2026-10-04: all 10 Dev Brain tests passed in isolation; all four required commit gates passed. See the accompanying logs. The full suite passed 314 application tests plus 8 tool tests; 237 hardware/integration tests remain explicitly ignored by the normal suite.