feat(session): add Cmd+K quick actions for search/model/thinking

packages/app/pr/cmdk-session-model-thinking.md

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+# Cmd+K Proof: Session Search, Model, Thinking
+
+## What was implemented
+
+- Added a `Cmd+K` quick actions entry point in session view.
+- Added root quick actions:
+  - `Search sessions`
+  - `Change model`
+  - `Change thinking`
+- Added session search mode with filtering and cross-session jump.
+- Added thinking mode with options (`None`, `Low`, `Medium`, `High`, `X-High`) that apply directly.
+
+## End-to-end proof (screenshots reviewed)
+
+I captured and reviewed each screenshot below to verify the flow works.
+
+### 1) Root quick actions are available via Cmd+K
+
+![Cmd+K root actions](./screenshots/cmdk-root-actions.png)
+
+Verified:
+- Command palette opens over session view.
+- Root actions show `Search sessions`, `Change model`, `Change thinking`.
+
+### 2) Search sessions flow works
+
+Session search mode:
+
+![Search sessions mode](./screenshots/cmdk-search-sessions.png)
+
+Filtered session search:
+
+![Filtered session search](./screenshots/cmdk-search-sessions-filtered.png)
+
+Verified:
+- `Search sessions` opens a dedicated session search mode.
+- Typing filters sessions by title.
+- Selecting a result closes the palette and switches to the chosen session.
+
+### 3) Change model flow works
+
+![Change model modal](./screenshots/cmdk-change-model.png)
+
+Verified:
+- `Change model` opens the model picker modal from Cmd+K.
+
+### 4) Change thinking flow works
+
+Thinking options mode:
+
+![Change thinking options](./screenshots/cmdk-change-thinking-options.png)
+
+Applied state (`Thinking High`):
+
+![Thinking High applied](./screenshots/cmdk-thinking-high-applied.png)
+
+Verified:
+- `Change thinking` opens a dedicated thinking mode in Cmd+K.
+- Selecting `High` updates composer state to `Thinking High`.
+
+## Notes on environment
+
+- Attempted `packaging/docker/dev-up.sh` in this worktree; orchestrator container was repeatedly killed (`exit 137`) during dependency install.
+- For UI validation, used this worktree's Vite app and connected it to an already-running healthy OpenWork Docker server.
+- Chrome MCP was used for the interactive verification and screenshot capture above.