feat(vscode): group agent work into one summary

[Gambit-Checkmate]

Summary

• Group each VS Code chat turn's thoughts, tool calls, edit cards, and task plan into one ordered collapsible work summary.
• Keep the final assistant response outside the summary and preserve the original activity order, including streaming and late tool updates.
• Report completed, stopped, and failed turn durations; reopen the summary when a pending approval needs attention.
• Return explicit cancelled/failed prompt outcomes from the extension host so the panel can render the correct terminal state.
• Add focused chat-panel harness coverage and fix the harness to load mention-utils.js in the same order as the real webview HTML.

The CLI UI and individual tool-card designs are unchanged.

Verification

• corepack pnpm test:format
• corepack pnpm test:types
• corepack pnpm test:lint
• corepack pnpm test:knip
• corepack pnpm test:audit
• Targeted VS Code panel/tool tests: 28 passed
• corepack pnpm run build:vscode

corepack pnpm test:ava was also attempted on Windows. The changed VS Code tests pass, while the root suite reports pre-existing Windows-only failures in Unix-path, symlink-permission, CLI subprocess/IPC, file-watcher, and terminal-rendering tests. plugins/vscode/src/acp-client.spec.ts remains excluded from the root AVA command because it requires the VS Code runtime; the changed path is covered by TypeScript checking and the extension build.

Closes #858

[akramcodez]

Hey @Gambit-Checkmate, could you please resolve the conflicts?

[Gambit-Checkmate]

Hey @Gambit-Checkmate, could you please resolve the conflicts?

Sure, I’ll resolve the conflicts with the latest main branch and push an updated commit. Thanks for pointing this out.

[Gambit-Checkmate]

Conflicts resolved in commit c3d439c, based on the latest main.\n\nThe conflict in plugins/vscode/media/chat-panel.js was merged by preserving both:\n- the work-summary aggregation and cleanup from this PR;\n- the upstream settings panel and settings message handling.\n\nI also fixed a duplicate MENTION_UTILS_SOURCE declaration exposed by the merge in source/vscode/chat-panel-harness.ts.\n\nValidation completed:\n- pnpm test:types\n- pnpm test:types:vscode\n- pnpm format:check\n- pnpm test:lint\n- VS Code extension build\n- 45 focused AVA tests covering chat-panel work summaries, tool cards, settings manager, and code lenses\n- changeset-check passed on CI\n\nThe PR is now mergeable; it is waiting for maintainer review.