fix(ui): align icon sizing and settings navigation hierarchy

[kev1n77]

Summary

• Normalize catalog and SVG icon sizing within shared component slots while preserving standalone icon sizes.
• Adjust the floating mini-chat icon size and add mixed-icon composition examples to Design Lab.
• Restore settings sidebar spacing and delegate navigation layout and selection styling to shared components.
• Distinguish group captions, normal navigation labels, and selected labels through color and font weight.
• Add regression coverage for icon slots, previews, navigation layout, selection, and search.

Fixes #

Type and Areas

Type: Bug fix / UI/UX / test

Areas: Web UI, shared UI component library, Design Lab

Motivation / Impact

Catalog icons could appear larger than adjacent SVG icons because component slots did not constrain both representations consistently.

The settings sidebar also had crowded spacing and competing local styles, while group captions and destination labels lacked sufficient visual distinction.

These changes improve visual consistency across production components and Design Lab, clarify navigation hierarchy, and preserve existing navigation and search behavior.

Verification

Passed during implementation; not rerun while preparing this PR:

• pnpm run check:web — passed appearance/theme checks and Web UI type checking.
• pnpm run design-system:check — passed builds, package checks, and tests, including 164 UI tests and 52 Design Lab tests.
• pnpm --dir src/web-ui exec vitest run src/app/scenes/settings/SettingsNavTypography.test.ts src/app/scenes/settings/SettingsNav.test.tsx src/app/scenes/settings/SettingsScene.test.tsx — 12 tests passed.

Checked while preparing this PR:

• git diff upstream/1.0.0-explore...HEAD --check — passed.

Actual application visual checks and remote workspace, remote control, Peer Device Mode, and Detached Dispatch scenarios were not exercised.

Reviewer Notes

• Icon sizing is owned by component slots; standalone icon defaults remain unchanged.
• Settings categories remain static navigation groups, not collapsible accordions.
• Typography uses existing theme tokens and retains high-contrast and forced-color handling.
• No backend, protocol, or persisted-data changes; no migration is required.
• Review mixed icon sizes and sidebar text hierarchy in light, dark, and inverse chrome.
• Run build-owning verification commands sequentially to avoid concurrent writes to shared generated outputs.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.