Let users toggle popup-card suggestion display from Settings and the menu

[FuJacob]

Summary

Builds on #347. That PR triggered the popup-card render mode automatically when caret geometry came back as .estimated. This PR adds a persistent global preference (Auto / Inline / Popup) so users can pin one style for every app, and surfaces the picker both in the Settings General section and the menu bar pop-up so it's reachable without opening Settings.

Validation

xcodegen generate                                  # no drift
swiftlint lint --quiet                             # exit 0
xcodebuild -project Cotabby.xcodeproj -scheme Cotabby \
  -destination 'platform=macOS' build              # ** BUILD SUCCEEDED **  (no warnings)
xcodebuild -project Cotabby.xcodeproj -scheme Cotabby \
  -destination 'platform=macOS' build-for-testing  # ** TEST BUILD SUCCEEDED **

Two new tests cover persistence (test_mirrorPreference_defaultsToAutoAndPersists) and the snapshot publisher (test_snapshotPublisher_emitsWhenMirrorPreferenceChanges). All existing snapshot/fixture call sites pick up the new field through a defaulted argument.

Local xcodebuild test execution hits the known Team ID code-signing mismatch on this machine (called out in CLAUDE.md). Tests compile correctly and need CI signing or Xcode UI to execute.

Risk / rollout notes

• Default is .auto, so existing users see identical behavior to Add mirror overlay fallback for unreliable caret geometry #347. Popup card still only appears for .estimated caret geometry unless the user pins .alwaysMirror.
• New mirrorPreference field on SuggestionSettingsSnapshot. Construction is centralized in two places (the model's snapshot getter and snapshotPublisher chain) and the shared test fixture; all sites updated.
• snapshotPublisher's contextToggles group went from CombineLatest to CombineLatest3 so the inner combine stack stays under Combine's 4-upstream cap; renamed to presentationToggles to reflect the wider scope.
• OverlayController now reads the preference live per showSuggestion call via a computed currentRenderModePolicy. Tests can still inject a fixed policy via the renamed renderModePolicyOverride: init parameter.
• Per-app overrides are intentionally still out of scope; the setCurrentBundleIdentifier plumbing stays dormant for a follow-up phase.

Linked issues

Refs #347.

Greptile Summary

Adds a persistent MirrorPreference setting (Auto / Inline / Popup) that lets users pin a suggestion display style globally, surfaced in both Settings and the menu bar. The default is .auto, preserving existing behavior for all current users.

• SuggestionSettingsModel stores and persists the preference via UserDefaults, threads it through snapshot and snapshotPublisher, and upgrades the inner CombineLatest to CombineLatest3 to stay within Combine's 4-upstream cap.
• OverlayController switches from a cached policy to a computed currentRenderModePolicy that reads the live setting on each showSuggestion call, so changes take effect immediately without any subscription bookkeeping.
• Two new tests cover default-value persistence and snapshot-publisher emission; the shared test fixture gains a defaulted mirrorPreference parameter so all existing call sites compile unchanged.

Confidence Score: 4/5

Safe to merge; the default is .auto so existing users are unaffected, and the new setting path is well-covered by tests.

The change is additive and backwards-compatible. The one notable issue is that helpDescription was added to MirrorPreference with the apparent intent of using it as per-item tooltips, but the UI never reads it — both pickers use hardcoded .help(…) strings instead. This leaves the property as dead code, but it has no runtime impact.

CompletionRenderModePolicy.swift — the unused helpDescription property warrants a quick follow-up (either wire it into the per-item .help() call or remove it).

Important Files Changed

Filename	Overview
Cotabby/Support/CompletionRenderModePolicy.swift	Adds Identifiable conformance and per-case displayLabel/helpDescription to MirrorPreference; helpDescription is dead code — never used by the UI.
Cotabby/Models/SuggestionEngineModels.swift	Adds mirrorPreference: MirrorPreference field to SuggestionSettingsSnapshot; straightforward additive struct change.
Cotabby/Models/SuggestionSettingsModel.swift	Adds mirrorPreference @Published property, persistence via UserDefaults raw-value string, setMirrorPreference mutator, and threads it through both the snapshot getter and snapshotPublisher (upgrading the inner CombineLatest to CombineLatest3). Logic is consistent and well-guarded.
Cotabby/Services/UI/OverlayController.swift	Replaces the stored renderModePolicy with a computed currentRenderModePolicy that reads the live mirrorPreference on each showSuggestion call; keeps the optional override seam for tests. Clean and correct.
Cotabby/UI/MenuBarView.swift	Adds a "Display" picker row wired through mirrorPreferenceBinding; mirrors the SettingsView implementation correctly.
Cotabby/UI/SettingsView.swift	Adds "Suggestion Display" picker in the General section with a Binding that calls setMirrorPreference; well-placed and consistent with other settings rows.
CotabbyTests/CotabbyTestFixtures.swift	Adds mirrorPreference: MirrorPreference = .auto to the shared snapshot fixture factory; all existing call sites pick it up transparently.
CotabbyTests/SuggestionAvailabilityEvaluatorTests.swift	Adds two new tests covering default persistence and snapshot-publisher emission on preference change; both use the established runOnMainActor + XCTestExpectation pattern correctly.

Sequence Diagram

sequenceDiagram
    actor User
    participant Settings/MenuBar as Settings / MenuBar
    participant SettingsModel as SuggestionSettingsModel
    participant UserDefaults
    participant OverlayController
    participant Policy as CompletionRenderModePolicy

    User->>Settings/MenuBar: Select display preference (Auto/Inline/Popup)
    Settings/MenuBar->>SettingsModel: setMirrorPreference(_:)
    SettingsModel->>SettingsModel: "mirrorPreference = preference"
    SettingsModel->>UserDefaults: persist rawValue string
    SettingsModel-->>Settings/MenuBar: "@Published emits (UI updates)"

    Note over SettingsModel: snapshotPublisher picks up change via CombineLatest3

    User->>OverlayController: (types, triggers suggestion)
    OverlayController->>OverlayController: currentRenderModePolicy (computed)
    OverlayController->>SettingsModel: read mirrorPreference live
    OverlayController->>Policy: mode(for: geometry, bundleIdentifier:)
    Policy-->>OverlayController: .inline or .mirror(reason:)
    OverlayController-->>User: Show ghost text or popup card

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Comments Outside Diff (1)

1. Cotabby/Support/CompletionRenderModePolicy.swift, line 33-45 (link)

   helpDescription is defined but never read

   The helpDescription property was added on MirrorPreference apparently for per-item tooltips, but neither SettingsView nor MenuBarView reference it — both views attach a single hardcoded .help(…) string to the whole Picker. The property is unreachable dead code as shipped.

   

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