fix(a11y): add focus-visible rings to outline settings segments + twistie

[mtskf]

Summary

• Add :focus-visible outline rings to .quoll-settings-segment (outline settings popover radiogroup) and .quoll-outline-twistie (heading expand/collapse button), mirroring the existing ring pattern used elsewhere (.quoll-outline-item:focus-visible).
• Previously both keyboard-focusable controls had no visible focus indicator, so arrowing between settings segments or focusing a twistie left keyboard users with no way to tell which control was focused.

Changes

• src/webview/styles.css: add :focus-visible { outline: 1px solid var(--vscode-focusBorder); } to .quoll-outline-twistie and .quoll-settings-segment.
• CHANGELOG.md / package.json: 0.1.44 patch bump + changelog entry.

Related

• TODO: a11y M2+L1 — focus-visible rings for outline settings segments + twistie (from .claude/docs/a11y/2026-07-12-editor-surface-audit.md)

Test Plan

• pnpm compile
• pnpm build
• pnpm test:unit (3327 passed)
• pnpm test:browser (26 passed)
• pnpm lint
• Verified in the real-browser preview harness (headless Playwright) that both .quoll-outline-twistie and .quoll-settings-segment render a 1px solid --vscode-focusBorder outline on :focus-visible.