fix(desktop): bound dense assistant file reference chips

.qwen/e2e-tests/electron-desktop/assistant-file-reference-overflow.md

@@ -0,0 +1,55 @@
+# Assistant File Reference Overflow
+
+- Slice date: 2026-04-26
+- Executable harness: `packages/desktop/scripts/e2e-cdp-smoke.mjs`
+- Command:
+  `cd packages/desktop && npm run e2e:cdp`
+- Result: pass
+- Artifact directory:
+  `.qwen/e2e-tests/electron-desktop/artifacts/2026-04-25T18-17-10-902Z/`
+
+## Scenario
+
+1. Launch the real Electron app with isolated HOME, runtime, user-data, and a
+   fake dirty Git workspace.
+2. Open the fake project through the desktop directory picker path.
+3. Send the first composer prompt and approve the fake command request.
+4. Wait for the fake ACP assistant response with repeated dense file
+   references.
+5. Assert the assistant message renders deduped chips, `:line:column` labels,
+   uncommon file references, and a compact overflow indicator.
+6. Continue the existing copy, retry, changed-files, review, settings,
+   terminal, and final layout smoke path.
+
+## Assertions
+
+- `README.md:1` appears as one file chip even though the assistant prose
+  repeats it.
+- `packages/desktop/src/renderer/App.tsx:12:5`, `.env.example`,
+  `Dockerfile`, `docs/guide.mdx`, and `src/App.vue` appear as accessible file
+  chips.
+- The overflow indicator shows `+2 more` with the accessible label
+  `2 more file references`.
+- File chips stay inside the assistant message and timeline, remain under the
+  maximum chip width, and do not create horizontal document overflow.
+- The assistant action row still exposes `Copy Response`, `Retry Last Prompt`,
+  and `Open Changes`.
+- Console errors: 0.
+- Failed local network requests: 0.
+
+## Artifacts
+
+- `assistant-message-actions.json`
+- `assistant-message-actions.png`
+- `assistant-retry-draft.json`
+- `resolved-tool-activity.json`
+- `conversation-changes-summary.json`
+- `completed-workspace.png`
+- `electron.log`
+- `summary.json`
+
+## Known Uncovered Risk
+
+This harness verifies the default 1240 px Electron window. A follow-up compact
+viewport pass should assert the same dense message state near the lower
+supported desktop width.