MVP completion gate verification + tag v0.1.0

[RE-codes]

Story

As a maintainer, the personal-use MVP is not done until every gate item passes. This is the close-out checklist.

Tasks

• npm test passes.
• npm run check (or tsc --noEmit) passes.
• Manifest is isDesktopOnly: true.
• All remaining items from plan/gfm-fragment-links-plan.md are complete or explicitly deferred.
• All P1, P2a, P2b rows in plan/observed-behavior-matrix.md are GREEN, MVP-accepted, or explicitly deferred.
• All P1/P2a/P2b QA rows in plan/QA-log.md are GREEN or marked deferred.
• Source-mode middle-click delay measured (≥10 samples) and either improved or accepted with the number recorded.
• README documents deferred limitations.
• No parser-shaped or broad gesture behavior added directly to the (now-thin) createEditorExtension().
• Tag a release: git tag v0.1.0 and (optionally) push.
• Update versions.json with the new version + minAppVersion.

Acceptance Criteria

• Every checkbox above is checked.
• Tag exists.
• Epic 14 closes.

References

• Parent epic: Epic: MVP Completion Gate #98
• plan/maintainability-plan-of-attack.md § MVP Completion Gate