Add runpane panes focus command (#401)

[ilijachrchev]

Description

Adds runpane panes focus command. Raises the Pane window, selects a pane, and optionally selects a specific panel within it.

Closes #401.

Follows the same pattern as panes rename / panes archive: contract.json -> generated artifacts -> CLI dispatch -> daemon handler -> renderer event.

New pieces: window-raising plumbing (show/restore/focus on BrowserWindow) and a pane:focus-requested IPC event that tells the renderer to call setActiveSession and setActivePanel.

Usage:

runpane panes focus --pane [--panel ] --source user|agent --yes [--json]

Requires --yes. Accepts --source agent|user. Archived/missing panes and mismatched panels return clear errors, never falls back to focusing something else. Doctrine text added to contract: agents invoke this only on explicit user request, never proactively.

Type of Change

• New feature (non-breaking change which adds functionality)
• Documentation update

Checklist

• I have read the CONTRIBUTING.md guidelines
• My code follows the code style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have run pnpm typecheck and pnpm lint locally
• I have tested the Electron app locally with pnpm electron-dev

Critical Areas Modified

• State management/IPC events

Screenshots (if applicable)

N/A. CLI command with no UI changes. The renderer-side change is a new IPC listener that calls existing store actions (setActiveSession, setActivePanel).

Additional Notes

5 new tests in runpane.test.ts: happy path, minimized window restore + panel selection, archived pane rejection, unknown pane rejection, panel-not-belonging rejection. All 64 existing tests pass (1 pre-existing skip).

Contract artifacts regenerated via pnpm run generate-runpane-contract. The 6 generated files were not hand-edited.

The handler sends pane:focus-requested via window.webContents.send() directly rather than through sendRendererEvent in events.ts, since the handler already holds the raised window reference. This matches how window:focus-changed is dispatched in index.ts.