chore(ui): bump @plannotator/ui to 0.39.0

[backnotprop]

Stacked on #1520 (merge that first; this PR then reduces to the bump). Publish is manual by the maintainer after merge, as always.

What 0.39.0 carries

• Element context on raw-HTML and live-app pinpoint annotations (feat(annotate): carry agent-facing element context on HTML and live-app pinpoints #1517): Annotation.elementContext / HtmlAnnotationTarget.context, parseHtmlElementContext on @plannotator/ui/components/html-viewer, elementContextExportBlock and exportAnnotationEntry on @plannotator/ui/utils/parser. The per-row Copy button briefly added to annotation cards is removed (fix(ui): remove the annotation panel's per-row Copy button #1520); panel chrome is unchanged from 0.38.2.
• Header decision primary without the inline count (fix(ui): drop the annotation count pill from the header decision primary #1516; internal, not host-supported surface).

Minor bump because the public Annotation type and the parser subpath gain new members.

For consumers

• @plannotator/core stays 0.25.2; nothing under packages/core changed. The core html-anchor host helpers do not carry elementContext yet (Carry elementContext through the core html-anchor host helpers (follow-up to #1517) #1521).
• Peer ranges unchanged from 0.38.2: react / react-dom ^19.2.3, tailwindcss as before, @codemirror/state ^6.7.2 beside @codemirror/view ^6.43.10.

Verification

• bun install (lockfile records the new workspace version, no dependency changes)
• bun run --cwd packages/ui smoke:package: "Verified @plannotator/ui@0.39.0 packs, resolves AnnotationPanel/Viewer/StickyHeaderLane/parser, and installs externally with @plannotator/core@0.25.2."

Publish (maintainer, after merge, from main)

cd packages/ui && npm publish

(prepack builds styles.css and the bridge assets; no --provenance locally; core is not republished.)