refactor: WelcomeViewModel, ERDiagram, ResultTabBar

[datlechin]

Summary

Second round of macOS HIG audit fixes, addressing MVVM layer violations, polling patterns, and remaining accessibility gaps.

WelcomeViewModel MVVM cleanup

• Extracted pendingConnectionShareURL and pendingDeeplinkImport from AppDelegate into PendingActionStore singleton — ViewModel no longer casts NSApp.delegate
• Replaced NSOpenPanel in ViewModel with .fileImporter modifier in View
• Replaced NSAlert in ViewModel with .alert modifier in View
• Moved window focus management to AppDelegate via .focusConnectionFormWindowRequested notification

ERDiagramViewModel reactive connection wait

• Replaced 500ms x 20 polling loop with notification-based wait using .databaseDidConnect
• Uses OSAllocatedUnfairLock for safe single-resume of CheckedContinuation
• 10-second timeout preserved as fallback

Quick UI fixes

• ResultTabBar: .onTapGesture replaced with Button for keyboard/VoiceOver accessibility
• HistoryPanelView: .listStyle(.plain) changed to .listStyle(.sidebar) per macOS HIG

Test plan

• Welcome window: create new connection, import connections from file, import from app — all sheets present correctly
• Welcome window: open a .tablepro share file — import sheet appears
• Welcome window: receive deep link import — sheet appears
• Welcome window: click "New Connection" when form window exists — it focuses correctly
• ER diagram: open on a connection that's still connecting — diagram loads after connection completes (no polling)
• Result tab bar: Tab + Return selects result tabs; close/pin/context menu still work
• History panel: sidebar-style list with inset selection appearance

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 2d5d6689a1

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Scope connection notification before resuming load

waitForConnection() resumes on any .databaseDidConnect event because the observer is registered with object: nil and the callback does not verify which connection actually finished. In this codebase those notifications are emitted globally (DatabaseManager+Sessions.swift and DatabaseManager+Health.swift), so a different session reconnecting can wake this continuation and make loadDiagram() fail with "No database connection" for the requested connectionId even though it is still connecting.

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Re-check driver after registering connect observer

This pre-check waits only once before subscribing, and waitForConnection() does not perform an immediate post-subscription driver check. If the target connection is established in the small window between this driver(for:) == nil test and observer registration, its connect notification is missed and the code unnecessarily waits for the full 10-second timeout before loading the diagram.

Useful? React with 👍 / 👎.