Refresh composer, agent icon, and composer trigger styling

[bharat-tf]

Applies the updated design for the composer area and the chrome triggers around it.

• ComposerShell: 12px corners, card surface, and a 1px violet->indigo gradient hairline drawn via the padding-box/border-box background-clip pair. The ramp and its glow are light-only; dark keeps the palette's neutral hairline, where the violet reads far louder than intended. ComposerContainer's dropzone radius follows so the drag ring stays flush.
• DraftCompositeSelector: the tools trigger loses its "Tools" caption and count badge, leaving an icon-only button (30px, matching the design). The count and name still reach assistive tech through the existing aria-label and sighted users through the tooltip. With both triggers now icon-only the row goes gapless so they cluster as one toolbar.
• AgentsLibraryButton: use the design system's own agent-2 glyph instead of the generic lucide robot.
• SaveAgentButton: squared-off chrome-action geometry (2px corners, 10px horizontal padding, card surface) applied at the component rather than the shared outline variant, since size classes are merged after variant classes and would otherwise win.
• agent-2.svg: currentColor in place of a hardcoded #000, which also makes the existing SubAgentCard usage legible in dark mode.

The composer radius is expressed directly rather than through --composer-radius, which still drives ThreadShell and UserMessageBubble; folding it into the theme preset would restyle surfaces this design did not touch.

Summary

Closes #

Changes

How was this tested?

Checklist

• I have read the contributing guidelines
• pnpm build, pnpm test, pnpm typecheck, pnpm lint:ci, and pnpm format:check pass locally
• Tests added/updated where it makes sense
• No hand-edits to generated code (packages/trueforge-sdk, .github/fern/openapi/openapi.json, docs/openapi.json) — fork PRs omit SDK regen; maintainers regenerate after merge
• Docs / .env.example updated if configuration or behavior changed

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Note

Low Risk
Mostly visual and layout tweaks plus test/config fixes; mobile users reach theme/settings via the nav drawer instead of the top bar.

Overview
Refreshes composer and surrounding chrome triggers to match the updated design.

The composer shell moves to 0.75rem corners, a card surface, a light-theme primary-token gradient hairline (faded top → solid bottom) with matching glow, and a neutral border in dark mode; the attachment dropzone radius follows so drag rings stay aligned. The tools control in the draft selector is icon-only (wrench); tool count and names stay on aria-label and the tooltip, and the trigger row is gapless so icon buttons read as one toolbar.

Agents library uses the agent-2 glyph instead of bot; agent-2.svg uses currentColor for dark-mode legibility. Save agent gets squared chrome-action styling (tight corners, card fill, extra horizontal padding). Sidebar mobile header no longer duplicates Settings / theme — those stay on the nav drawer / rail footer; mobile drawer chrome drops some divider borders. Tests expect a single Settings/theme instance; Vitest passes --no-webstorage on Node 25+ so jsdom owns localStorage.

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🦋 Changeset detected

Latest commit: 565ecc1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@truefoundry/trueforge-ui	Patch

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