SettingsStore — disposition for remaining @AppStorage / UserDefaults sites

[eyelock]

Follow-up to refactor/settings-store (which migrated Tier A — the four audit-named drift fields — and Tier B — seven other globals already on SettingsStore). Tracks every remaining direct settings call site and what should happen to it.

Migrate to SettingsStore (next PR — ~25 LOC total)

• copyOnSelect — SettingsView.swift:39, TerminalHostView.swift:472. Same shape as the four named fields.
• defaultWorkingDirectory — SettingsView.swift:40, BoardViewModel.swift:697. Same shape, default NSHomeDirectory().
• diagnosticsVerboseMode — TermQLogBuffer.swift:14, 18, 22. Removes the only direct-UserDefaults pair in the diagnostics service.

Move to a different owner (each its own PR, mostly small)

• marketplaceAutoRefresh → MarketplaceStore (1 site).
• defaultHarnessAuthorDirectory → HarnessAuthorPreferences or onto HarnessAuthor (5 sites: HarnessWizardSheet, ForkHarnessSheet, DuplicateHarnessSheet, SettingsMarketplacesView, HarnessesSidebarTab).
• sidebar.selectedTab → WorktreeSidebarViewModel or a small SidebarState (3 sites: SidebarView, HarnessDetailView, HarnessWizardSheet — three Views coordinating via @AppStorage is fragile).
• protectedBranches → dedicated GitConfigStore or stays on WorktreeSidebarViewModel. Not user-pref-shaped; don't fold into SettingsStore.

Stays as-is (justified, no action)

• dismissedTmuxSessions — runtime state on BoardViewModel+TmuxRecovery, not a preference.
• repositories (expanded-repo / expanded-branch keys) — sidebar tree state on WorktreeSidebarViewModel. Could become @SceneStorage, not store-bound.
• feature.harnessTab — feature flag. Move to a FeatureFlags type when there's a second flag.
• sidebarCollapsed — ephemeral UI state on ContentView. Could become @SceneStorage.
• SUAutomaticallyChecksForUpdates, SUIncludeBetaReleases — Sparkle-owned key names; we read but don't take ownership.
• AppleLanguages — Cocoa system pref, mirrored from preferredLanguage.
• preferredLanguage — paired with AppleLanguages in SupportedLanguage. Migration possible but low value.
• BackupManager.Keys.* (backupFrequency, backupRetentionCount, lastBackupDate) — backup-domain, self-contained.
• GlobalEnvironmentManager.storageKey — encrypted env-var blob.
• YNHDetector.ynhHomeOverrideKey, capabilitiesMinOverrideKey — debug-only overrides.
• DataDirectoryManager.userDefaultsKey — install config, runs at startup.
• MarketplaceStore.defaultsSeedKey — first-run seed flag.

Pre-existing inconsistency (its own issue/PR, user-visible)

TerminalHostView.allowOscClipboard (Sources/TermQ/Views/TerminalHostView.swift:192) defaults to true when unset, while SettingsStore.Defaults.allowOscClipboard is false (matching SettingsView's pre-PR default). After this PR, SettingsView reads through the store; TerminalHostView still reads UserDefaults directly with a default-true fallback. So a never-touched user sees "Off" in Settings but TerminalHostView's runtime gate returns true until they explicitly toggle.

This is pre-existing — the audit didn't catch it, and it's beyond "drift fix" scope. Recommended fix: migrate TerminalHostView to SettingsStore.shared.allowOscClipboard, decide whether to preserve the default-true behavior for existing users via a one-shot migration, and CHANGELOG it. Worth its own issue.

[eyelock]

Tier C quick wins landed in #266 (copyOnSelect, defaultWorkingDirectory, diagnosticsVerboseMode). The four "move to different owner" items are now tracked in #269 — they're owner-extraction refactors, not SettingsStore work. The OSC 52 default-mismatch is being fixed directly. Closing this disposition tracker.