chore: release v0.28.0

[mmcky]

Release prep for v0.28.0, per the AGENTS.md release checklist (steps 1–4): [Unreleased] promoted to [0.28.0] - 2026-09-03, an entry added for the one merge since v0.27.0 without one (#299, experiment archive), version bumped in package.json/package-lock.json, .dev/STATE.md in-flight updated (W1 #259 retargets to v0.29.0), dist-action/ rebuilt so the bundle reports engineVersion: 0.28.0.

Headline: the Malayalam editor's ml#12 answers are encoded, and exercise-family blocks in ml are byte-identical to the source by construction (#303). Release notes are staged in .dev/scratch/release-notes.md.

After merge, per §4a: tag v0.28.0 on the merge commit → E2E-gate the tag (--action-ref v0.28.0, now 28 scenarios × 3 lanes) → move v0.28 and v0 → @v0 smoke (scenario 01) → GitHub release titled v0.28.0.

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[Copilot]

🟡 Changes recommended

CHANGELOG.md is missing a new top-level [Unreleased] section, which risks future entries being added under the released 0.28.0 heading.

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Pull request overview

Prepares the repository for the v0.28.0 release by bumping the npm package version and promoting the changelog entry to the release date, aligning with the documented release workflow.

Changes:

• Bump package version from 0.27.0 → 0.28.0 in package.json and package-lock.json.
• Promote the changelog section to ## [0.28.0] - 2026-09-03 and add an entry for #299.

File summaries

File	Description
package.json	Bumps the package version to 0.28.0.
package-lock.json	Keeps lockfile metadata in sync with the 0.28.0 version bump.
CHANGELOG.md	Promotes the top section to the 0.28.0 release entry and records release notes.

Review details

• Files reviewed: 3/4 changed files
• Comments generated: 1
• Review effort level: Lite

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[mmcky]

§4a gate — completed 2026-09-03. Tag v0.28.0 = 9284fbc. E2E on the tag: 84/84 sync runs success (28 scenarios × 3 lanes; the 6 skipped are non-matching triggers), 28/28 translation PRs per lane, 28/28 verdicts per lane at engineVersion: 0.28.0 / engineRef: v0.28.0. Scenario 28 on the .ml lane (test-translation-sync.ml#126) delivered both exercise blocks byte-identical (11/11, 16/16 lines), PASS / auto-merge. Floating tags moved: v0.28 and v0 → 9284fbc. Alias smoke (scenario 01 at @v0): all three lanes report engineVersion: 0.28.0 / engineRef: v0. GitHub release: https://github.com/QuantEcon/action-translation/releases/tag/v0.28.0