refactor(ui): frame chat flow cards with coss-ui Frame headers (CODE-381)

[Zerlight]

Summary

Closes CODE-381.

Chat-flow cards (code block, terminal, file/tool previews, edited-files rollup) hand-rolled their header chrome as Card + CardHeader with bg-muted/border-b overrides. This converts them to the coss-ui Frame pattern — a borderless muted tray (Frame) with the card's upper part in the tray header (FrameHeader) and content in the inset panel (FramePanel) — via new shared chat-density slots in chat/chat-card.tsx (ChatCardHeader/ChatCardTitle/ChatCardActions/ChatCardPanel, density overrides only).

Converted surfaces: CodeBlock, ArtifactFrame (+ FenceFallback), Terminal + TerminalBlock, FilePreviewCard (DiffBlock follows), ToolPreviewCard, TurnDiffSummary. Showcase-only cards (test-results, schema-display, artifact, web-preview, package-info, queue, step, commit, stack-trace) are deliberately left on Card chrome until they're wired.

Design refinements from review:

• Frame-header labels are sans; only terminal/execute headers keep mono for the command they display.
• Copy buttons: code blocks copy their source (now built-in, so tool-result JSON/HTML blocks get one too); terminal headers copy the executed command only — threaded to the live adapter as a new optional command prop on TerminalBlock/RuntimeTerminalBlock.
• Mutation receipts ("The file … has been updated successfully") render as plain prose under the diff instead of a second preview card.
• Turn-diff rows show the file-identity icon + basename with the full path in a hover tooltip; no divider lines; the show-more chevron points down/up (expand/collapse) instead of the tree-node right→down.
• Terminal fixes along the way: TerminalBlock no longer double-renders a header, the ANSI surface is clipped to the panel radius (was square-cornered and theme-mismatched in dark mode), and trailing PTY/stdout newlines no longer render as blank panel space (regression test added).

The chrome contract test (card-radius.test.tsx) now asserts the frame slot with a <header> row per card.

Verification

• pnpm check:ci and pnpm test (1772) pass on the rebased branch.
• Drove the webview dev:mock conversation showcase headless (playwright-core + Chrome): code fence, file read/write cards, diff card, search card, artifact frames (mermaid/svg/html), execute terminals, and the PTY terminal block all render the borderless tray + inset panel, with the expected header fonts and copy buttons; mutation receipt renders as prose under the diff.
• TurnDiffSummary doesn't render in the mock (its stream never completes a turn with edits), so its rows are covered by unit tests plus live review over HMR against a real session.

Checklist

• pnpm check:ci and pnpm test both pass (plus cargo fmt / clippy / test for Rust changes)
• I ran the affected surface and observed the change working
• If a wire message changed: WIRE_PROTOCOL_VERSION is bumped — no wire changes
• New code and assets are my own work, or their origin and license compatibility are noted above
• Docs and comments are updated where behavior changed

[linear-code]

CODE-381

[greptile-apps]

Greptile Summary

This PR moves core chat-flow cards to the shared coss-ui Frame pattern. The main changes are:

• Shared compact header, title, action, and panel components for chat cards.
• Frame-based code, artifact, terminal, file, tool, and edit-summary surfaces.
• Copy actions for code and terminal commands.
• Updated terminal output trimming that preserves meaningful trailing spaces.
• Refined file labels, tool receipts, and edit-summary rows.

Confidence Score: 5/5

This looks safe to merge.

The terminal cleanup now removes only trailing newline characters. Meaningful trailing spaces remain visible. No blocking issues were found in the updated code.

T-Rex Logs

What T-Rex did

• I reviewed the before-change and current videos that illustrate the real scrolling conversation and representative code, and I noted the inline artifact surfaces.
• I executed a browser session with Vite, confirmed there were no page errors, and verified that the styled Workbench UI rendered.
• I gathered and attached the capture script, process output, browser logs, screenshots, posters, and videos for review.

_{Ran code and verified through T-Rex}

Important Files Changed

Filename	Overview
packages/presentation/ui/src/chat/terminal.tsx	Moves terminal rendering to Frame chrome and preserves trailing spaces while removing blank tail lines.
packages/presentation/ui/src/chat/terminal-block.tsx	Uses the shared terminal frame header and adds optional command copying.
packages/presentation/ui/src/chat/chat-card.tsx	Introduces shared compact Frame slots for chat-flow cards.
packages/presentation/ui/src/chat/code-block.tsx	Converts code blocks to Frame chrome and adds built-in copy actions.
packages/presentation/ui/src/chat/file-preview-card.tsx	Converts file previews to Frame chrome with basename labels and path tooltips.

_{Reviews (5): Last reviewed commit: "chore(lint): clear sukka 8.14 warnings o..." | Re-trigger Greptile}

[Zerlight]

Example pictures of Frame-card components: