Make beta release artifacts reproducible on Linux and Android

Constraint: SRS-118 and SRS-119 require a Linux release package and an Android release AAB, and the current workspace also needs the sibling oboe-rs checkout for Cargo manifest loading.
Rejected: Keep release packaging as ad-hoc local knowledge | CI and contributors would still miss the required artifacts and hit the missing oboe-rs prerequisite.
Confidence: medium
Scope-risk: moderate
Directive: If the oboe-rs fork path changes or is vendored, update the helper scripts and workflow checkout steps together.
Tested: bash -n tools/build-linux-deb.sh tools/build-android-aab.sh; python3 YAML parse for .github/workflows/ci.yml, .github/workflows/bench-advisory.yml, .github/workflows/bench-baseline-update.yml; git diff --check
Not-tested: End-to-end flutter build linux --release; end-to-end flutter build appbundle --release; GitHub Actions runtime execution

.github/workflows/bench-baseline-update.yml

@@ -18,6 +18,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Checkout oboe-rs fork
+        run: git clone --depth 1 https://github.com/edisonjwa/oboe-rs.git ../oboe-rs
       - name: System deps (cpal / Opus)
         run: |
           sudo apt-get update