chore: release v0.28.1

[mmcky]

Release prep for v0.28.1, per the AGENTS.md release checklist (steps 1–4): [Unreleased] promoted to [0.28.1] - 2026-09-14 with a fresh empty [Unreleased] header above it, version bumped in package.json/package-lock.json, .dev/STATE.md in-flight updated, a .dev/log/ entry for the incident. dist-action/ rebuilt and byte-identical (the bundle reads the version from package.json at runtime).

Headline: sync mode fires only for PRs merged into the default branch (#308). A theme migration merged into lecture-python-programming's long-lived jb2 branch on 2026-09-12 opened translation PRs in three target repos for unpublished content; every published sync template now carries branches: [main], and the action skips a merged PR whose base is not the repository's default branch on both the pull_request and \translate-resync paths. Release notes are staged in .dev/scratch/release-notes.md.

After merge, per §4a: tag v0.28.1 on the merge commit → E2E-gate the tag (--action-ref v0.28.1, 28 scenarios × 3 lanes) → move v0.28 and v0 → @v0 smoke (scenario 01) → GitHub release titled v0.28.1. Gate tally will be recorded here.

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[Copilot]

🟢 Approval recommended

Changes are straightforward release bookkeeping (version bump + changelog/state/log updates) and are internally consistent.

Pull request overview

Prepares the repository for the v0.28.1 release by promoting the changelog entry, bumping the npm package version, and recording release state/incident notes under .dev/ (following the repo’s release workflow).

Changes:

• Bump version from 0.28.0 → 0.28.1 in package.json and package-lock.json.
• Promote CHANGELOG.md’s [Unreleased] content into a dated [0.28.1] - 2026-09-14 section, leaving an empty [Unreleased] header.
• Update .dev/STATE.md verification date and add a .dev/log/ incident/release entry for the jb2 sync fallout context.

File summaries

File	Description
package.json	Bumps package version to 0.28.1.
package-lock.json	Keeps lockfile/package metadata version in sync at 0.28.1.
CHANGELOG.md	Promotes the release notes into a new 0.28.1 section dated 2026-09-14.
.dev/STATE.md	Updates verified date and records the v0.28.1 release in-flight status.
.dev/log/2026-09-14-jb2-sync-fallout.md	Adds an incident/release log entry documenting the jb2-triggered sync fallout and remediation.

Review details

• Files reviewed: 4/5 changed files
• Comments generated: 0
• Review effort level: Lite

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[mmcky]

§4a gate — completed 2026-09-14. Tag v0.28.1 = 3de9024. E2E on the tag (harness start 03:29:56Z): 84/84 sync runs success (28 scenarios × 3 lanes; the 3 skipped are the non-matching-trigger closes), 28/28 translation PRs per lane, 28/28 verdicts per lane at engineVersion: 0.28.1 / engineRef: v0.28.1. The harness fires its labeled trigger on open fixture PRs against main, so the new branches: [main] filter was exercised on every run. Floating tags moved: v0.28 and v0 → 3de9024. Alias smoke (scenario 01 at @v0, start 03:36:11Z): 3/3 pull_request runs success, one translation PR per lane (test-translation-sync.zh-cn#876, .fa#260, .ml#160), each verdict engineVersion: 0.28.1 / engineRef: v0. GitHub release published: https://github.com/QuantEcon/action-translation/releases/tag/v0.28.1.

Tidy-up outside the repo: lecture-python-programming.fr#79, .fa#166, .zh-cn#105 closed unmerged; branches: [main] PRs open on the deployed workflows — QuantEcon/lecture-python-programming#630, QuantEcon/lecture-python-intro#846, QuantEcon/lecture-python.myst#1056.