[jcwal1516]

Opens the 0.13.1 patch release: the CPU batch region fixes (#299, #298), the Metal zero-bitplane seed, the classic Tier-1 decode speedups, and the other fixes merged since v0.13.0, as listed in the changelog.

• The workspace and its exact internal pins move to 0.13.1, and the changelog heading is ## [0.13.1] - 2026-10-29. That date must equal the tag date, so if the tag slips past today the heading needs a new commit.
• The semver baseline moves to v0.13.0 (50124262). The 0.13.1 report and review compare with that tag, and the 0.13.0 report and review return to their tagged contents.
• No ordinary API item changed in any package. j2k-native adds five rustdoc-hidden items: ComponentRowSink with write_rows and Image::decode_region_rows_for_integer_output_with_context (perf(j2k-native): stream serial region rows to a sink #294), and window_referenced_classic_plan_to_stores / window_referenced_htj2k_plan_to_stores (fix(j2k): CPU batch regions of large images and at rounded tile edges #301). The break ledger is empty, so j2k = "0.13" users get 0.13.1 from cargo update.
• The fuzz lockfiles also gain dependencies their manifests already required but the locks never recorded: j2k-core's libc and windows-sys since 0.13.0, and in the j2k-t803 fuzz lock the zip 9 that the workspace requires, replacing a stale 8.6.0 entry. Each new entry uses the root lock's version.
• README, SECURITY, xtask/RELEASING.md and the stable API page list 0.13.1 as being prepared; they still name 0.13.0 as the published release, as the docs policy requires until the new tag exists.

Testing

• cargo xtask semver, cargo xtask release-integrity, cargo xtask release-integrity --publish, cargo fmt --all -- --check, cargo xtask repo-lint, cargo test -p xtask --locked pass.
• Every fuzz lockfile resolves with cargo metadata --locked --offline.

Release steps after merge

Full validation on the merge commit, one gpu-validation.yml run with target=all mode=full (the CUDA runner is back, so no waiver), cargo xtask release-status --sha <merge> --scope all, then the annotated v0.13.1 tag and the publish workflow.