refactor(cockpit): polish — chat lib data-theme, token migration, border standardization

[blove]

Summary

First in a three-PR sequence (spec: `docs/superpowers/specs/2026-05-13-cockpit-polish-design.md`, plan: `docs/superpowers/plans/2026-05-13-cockpit-polish.md`).

• Chat lib theme attribute rename: `[data-ngaf-chat-theme]` → `[data-theme]` in both `chat-tokens.ts` (TS-injected) and `chat.css` (global stylesheet). Aligns with Tailwind v4 / shadcn / Storybook conventions. The lib's existing three-layer cascade (`:root` default → `prefers-color-scheme` override → `[data-theme]` programmatic override) is preserved — only the override attribute name renames. Breaking for any external consumer that set the old attribute; we're 0.0.x so a patch bump is sufficient signal.
• `installEmbeddedTheme` cleanup: drop the in-flight `dataset.ngafChatTheme` set. After the chat lib rename, `data-theme` covers both design-tokens and chat lib theming.
• `cockpit.css` token migration: drop dead `@theme inline` block (13 lines, no Tailwind utility consumed it) and unused shadcn alias `:root` block (14 lines). Replace 11 hardcoded `rgba(0, 64, 144, X)` and the single `rgba(26, 27, 38, 0.95)` literal with `--ds-*` tokens — code blocks and callouts now theme correctly in light AND dark. Net cockpit.css: -30 lines.
• Border standardization: migrate 6 inline `style={{ borderBottom: ... }}` / `borderRightColor` / `borderLeft` sites in cockpit components to Tailwind arbitrary-value classes (`border-b border-[var(--ds-border)]`). Consistent with cockpit's dominant Tailwind-arbitrary-value pattern. Includes preserving layout-stability in `navigation-groups.tsx` (transparent border on inactive branch).

PR 2 (chat lib polish — text-wrap bug + bubble width handling) and PR 3 (cockpit ↔ website style alignment) follow.

Test plan

• `pnpm nx run-many -t lint,test -p design-tokens,ui-react,example-layouts,chat,cockpit` — green
• `pnpm nx e2e cockpit` — verified via CI on this PR (local was blocked by .next dev lock contention with running dev server)
• `pnpm nx build website` — green
• `pnpm nx build cockpit-chat-timeline-angular` — green
• Manual chrome MCP smoke (pre-PR): chat input flips with host theme; no white callouts in cockpit dark; no dark code-block headers in light

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
cacheplane	Ready	Preview, Comment	May 14, 2026 0:12am