Homes the orphaned cowriting.pinDiffBaseline command and gives the writer a
reachable Pin control in the preview toolbar. Per spec §7.2 SLICE-1
(docs/superpowers/specs/2026-06-12-f11-preview-toolbar-interaction-surface.md).
- trackChangesPreview: extract onDidReceiveMessage into handleWebviewMessage;
add the F11 `pinBaseline` intent → DiffViewController.pin(previewedDoc) (the
bound doc, not activeTextEditor — §6.7); ToolbarMsg union; receiveMessage test
seam exercising the real message→seam wiring (INV-35).
- webview: ⌖ Pin baseline button in #cw-header posting { type: "pinBaseline" };
theme-aware toolbar-button CSS (light/dark/high-contrast, disabled state).
- package.json: unhide pinDiffBaseline — commandPalette `when` false →
editorLangId == markdown (resolves the #34 orphan from the command side).
- host E2E (test/e2e/suite/f11Toolbar.test.ts): pinBaseline message clears the
change-marks + advances the baseline to `pinned`; palette `when` is reachable.
Also archives the F11 implementation plan to docs/superpowers/plans/.
197 unit + 47 host E2E green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Ben Stull