docs(backlog): close B-0273 as pure drift — safe/unsafe ROM split shipped in #5874

docs/BACKLOG.md

@@ -148,7 +148,7 @@ are closed (status: closed in frontmatter)._
 - [x] **[B-0270](backlog/P1/B-0270-pm2-role-skill-definition-2026-05-08.md)** PM-2 role - skill definition + persona agent
 - [x] **[B-0271](backlog/P1/B-0271-pm2-first-research-pass-2026-05-08.md)** PM-2 role — first research pass on Zeta feature gaps
 - [x] **[B-0272](backlog/P1/B-0272-atari-rom-canonical-naming-tosec-lookup-2026-05-08.md)** Atari 2600 ROM canonical naming via TOSEC/No-Intro hash lookup
-- [ ] **[B-0273](backlog/P1/B-0273-atari-rom-safe-unsafe-folder-split-2026-05-08.md)** Atari 2600 ROM safe/unsafe folder split for license compliance
+- [x] **[B-0273](backlog/P1/B-0273-atari-rom-safe-unsafe-folder-split-2026-05-08.md)** Atari 2600 ROM safe/unsafe folder split for license compliance
 - [ ] **[B-0274](backlog/P1/B-0274-pages-astro-workflow-scaffold-and-sha-pinning-2026-05-08.md)** Pages discoverability - Astro workflow scaffold and SHA pinning
 - [ ] **[B-0275](backlog/P1/B-0275-pages-astro-http-200-and-deploy-validation-2026-05-08.md)** Pages discoverability - Astro deploy validation and HTTP 200 check
 - [x] **[B-0276](backlog/P1/B-0276-structure-recognizer-fingerprint-library-2026-05-08.md)** Structure recognizer — fingerprint library for codebase shapes

docs/backlog/P1/B-0273-atari-rom-safe-unsafe-folder-split-2026-05-08.md

@@ -1,13 +1,14 @@
 ---
 id: B-0273
 priority: P1
-status: open
+status: closed
 title: "Atari 2600 ROM safe/unsafe folder split for license compliance"
 created: 2026-05-08
-last_updated: 2026-05-08
+last_updated: 2026-05-29
+closed: 2026-05-29
 parent: B-0083
 depends_on: [B-0272]
-classification: blocked-on-B-0272
+classification: buildable-now
 decomposition: atomic
 type: friction-reducer
 ---
@@ -24,3 +25,35 @@ After canonical naming, split ROMs into:
 - safe/ folder not gitignored, checked in
 - unsafe/ folder gitignored
 - README documents which ROMs are safe to distribute
+
+## Resolution (2026-05-29)
+
+Closing as **PURE DRIFT** (class #1) per the `backlog-item-start-gate.md`
+step-0 substrate-drift discriminator. The dependency B-0272 closed
+2026-05-16; this row's `classification` was never updated off the stale
+`blocked-on-B-0272`. All 3 acceptance items verifiably shipped:
+
+| Acceptance | Status |
+|---|---|
+| safe/ folder not gitignored, checked in | shipped — `roms-safe/README.md` + `roms-safe/atari/2600/README.md` tracked; the gitignore at `roms/.gitignore` governs only `roms/`, so `roms-safe/` is checked in by default |
+| unsafe/ folder gitignored | shipped — `roms/` stays gitignored via the existing depth-limited rule (`*` + `!*/` + sentinel re-includes); only README sentinels tracked |
+| README documents which ROMs are safe to distribute | shipped — `roms-safe/README.md` explains the split; `roms-safe/atari/2600/README.md` carries a per-ROM table (canonical name, author, license class, citation) for 7 homebrew titles |
+
+Provenance:
+
+- All artifacts shipped via PR [#5874](https://github.com/Lucent-Financial-Group/Zeta/pull/5874)
+  (`feat(roms): Add tooling for safe/unsafe ROM split (B-0273)`),
+  merged 2026-05-29T10:08:47Z at `75802ccb528ad57b61b0c9f87c191b773d2f08b8`.
+- Tooling beyond the 3 acceptance items also landed in the same PR:
+  `tools/roms/split-by-license.ts` (+ `.test.ts`, allowlist-driven,
+  report-only by default with `--apply`) and
+  `tools/roms/manifests/atari-2600-allowlist` (one canonical filename per
+  line, per-ROM license citation in comments).
+- `split-by-license.ts` header comment self-identifies: "Part of B-0273."
+
+Implementation-PR (#5874) shipped the code but left this row `status: open`
+— the implementation-doesn't-close-the-row drift pattern that the step-0
+discriminator catches. Mirrors sibling B-0272's pure-drift close (closed
+2026-05-16). Verification: existence-check of all 4 artifacts on `origin/main`
++ `git merge-base --is-ancestor` confirming #5874's merge commit reachable +
+per-acceptance-criterion read of the tracked READMEs and `roms/.gitignore`.