Add refresh button to menu-bar Model row

[FuJacob]

Summary

Adds an arrow.clockwise refresh button next to the folder shortcut in
the menu-bar Model row so users can rescan the Models folder without
opening Settings or relaunching. The picker label now truncates
middle-style so the second icon fits without crowding longer model names.

Validation

xcodebuild -project Cotabby.xcodeproj -scheme Cotabby -destination 'platform=macOS' build
# ** BUILD SUCCEEDED **

xcodebuild -project Cotabby.xcodeproj -scheme Cotabby -destination 'platform=macOS' build-for-testing
# ** TEST BUILD SUCCEEDED **

swiftlint lint --quiet Cotabby/UI/MenuBarView.swift
# exit 0

Did not run the UI end-to-end — change is a one-button wire-up using the
exact two-call refresh pattern already used by SettingsView.refreshModels().

Linked issues

None.

Risk / rollout notes

• Same two-call refresh as SettingsView (modelDownloadManager.refreshModelStates() +
  runtimeModel.refreshAvailableModels()), so behavior matches the existing path.
• Both refresh calls are synchronous and cheap; no debounce needed.
• The new icon eats ~26pt of row width. Picker label gains .lineLimit(1)
  • .truncationMode(.middle) so longer filenames (e.g.
    Qwen3-0.6B-Q4_K_M.gguf) truncate gracefully instead of pushing the
    icons off-row.

Greptile Summary

This PR adds a refresh button (arrow.clockwise) alongside the existing folder shortcut in the menu-bar Model row, letting users rescan the local model directory without opening Settings. It also applies .frame(maxWidth: .infinity) to the Picker — the correct way to prevent long filenames from pushing trailing icons off-row on AppKit's native popup button — and includes a /// comment explaining why per-item text modifiers are unreliable in this context.

• Refresh button: calls modelDownloadManager.refreshModelStates() + runtimeModel.refreshAvailableModels(), mirroring the exact two-call sequence already used by SettingsView.refreshModels() and WelcomeView.
• Picker layout fix: .frame(maxWidth: .infinity) constrains the Picker to fill remaining row width, matching the approach endorsed in the code comment and consistent with the rest of the layout hierarchy inside the fixed-width (340 pt) menu panel.

Confidence Score: 5/5

Safe to merge — the change is a one-button wire-up that delegates to two well-established synchronous refresh calls, with no new state or side-effect paths.

Both refreshModelStates() and refreshAvailableModels() are synchronous, @MainActor-confined, and called identically in SettingsView and WelcomeView. The .frame(maxWidth: .infinity) layout fix is correct and well-documented. No new async work, no new state, no error paths added.

No files require special attention.

Important Files Changed

Filename	Overview
Cotabby/UI/MenuBarView.swift	Adds a refresh button and .frame(maxWidth: .infinity) to the Picker in modelRow; both changes are correct, well-documented, and consistent with the existing codebase patterns.

Sequence Diagram

sequenceDiagram
    actor User
    participant MenuBarView
    participant ModelDownloadManager
    participant RuntimeBootstrapModel
    participant LlamaRuntimeManager

    User->>MenuBarView: Tap refresh button
    MenuBarView->>ModelDownloadManager: refreshModelStates()
    Note over ModelDownloadManager: Re-checks download tasks and file presence
    MenuBarView->>RuntimeBootstrapModel: refreshAvailableModels()
    RuntimeBootstrapModel->>LlamaRuntimeManager: refreshAvailableModels()
    Note over LlamaRuntimeManager: Re-scans runtime directories for GGUF files
    LlamaRuntimeManager-->>RuntimeBootstrapModel: availableModels updated
    RuntimeBootstrapModel-->>MenuBarView: ObservedObject triggers re-render
    MenuBarView-->>User: Picker shows updated model list

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_{Reviews (2): Last reviewed commit: "Constrain model Picker frame instead of ..." | Re-trigger Greptile}