implement-spec

Implement the specified phase of the given spec file. Ultrathink. Follow these steps: ## 1. Read and understand the spec Read the entire spec file. Understand the problem overview, solution overview, goals, and non-goals. Pay close attention to the phase you've been asked to implement. ## 2. Read all important files Read every file listed in the "Important files/docs/websites for implementation" section of the spec. Also read any external documentation links. Do not start writing code until you thoroughly understand the existing codebase and how your changes fit in. ## 3. Implement the phase Work through every task item in the phase, including all success criteria (tests, typechecks, lint checks). A phase is not complete until every task item is done, including running any verification steps. Run `pnpm run typecheck`, `pnpm test`, and `pnpm run lint` after implementation to catch issues. ## 4. Verify goals Check the spec's Goals section. If the phase you just implemented should complete any of those goals, explicitly verify them through integration tests or manual testing of the Electron app using Playwright (see AGENTS.md for Playwright instructions). Do not consider the phase done until achieved goals are verified end-to-end. ## 5. Mark tasks complete Mark all completed task items in the spec as done (`- [x]`) before presenting to the user. ## 6. Do not commit When you're done, do **not** stage or commit your changes. Present the completed work to the user for...