RepositorySettings: whole-snapshot .binding writeback reverts externally written openActionID

[onevcat]

Problem

RepositorySettingsFeature's case .binding writes the entire RepositorySettings snapshot back to @Shared(.repositorySettings(rootURL)) (RepositorySettingsFeature.swift:373-400). Meanwhile AppFeature writes openActionID directly into the same shared storage from the main-window toolbar (AppFeature.swift:559-585) without syncing the open Settings pane's snapshot. Notably, AppFeature.swift:850-854 does sync runScript for exactly this reason — the hazard is known but inconsistently handled.

Failure scenario

1. Open Settings → some repository pane (snapshot captured).
2. In the main window toolbar, pick a new "Open in" app (openActionID written to @Shared).
3. Toggle anything in the still-open Settings pane.
   → The stale snapshot (old openActionID) is written back wholesale; the toolbar pin silently reverts.

Suggested fix

Either sync state.settings.repositorySettings?.settings.openActionID in .openActionSelectionChanged / .openActionResetToAutomatic (mirroring the runScript handling), or make the .binding writeback field-targeted (compare setGlobalCommandEnabled, RepositorySettingsFeature.swift:233-244).

Origin

TCA-conventions audit of the Settings area (2026-07-30), agent finding — not yet re-verified line by line; confirm the exact write sites before fixing.