fix(editor): focus the SQL editor when opening a new tab (#1765)

[datlechin]

Fixes #1765.

Problem

Opening a new SQL editor tab with ⌘T often put keyboard focus in the sidebar "Filter" search field instead of the editor, so typed SQL went into the filter. Reliable repro: connect, ⌘T (focus correct), ⌘T again, focus jumps to the filter field. It also happens with no tabs open when the filter field already has focus.

Root cause

A new tab's window never sets initialFirstResponder, so AppKit auto-assigns focus to the geometrically-leading focusable view (the sidebar filter field) when the window becomes key. SQLEditorCoordinator.prepareCoordinator() tried to claim focus 50ms later, but only when window.firstResponder == nil || === window, so it backed off the moment the filter field already held focus. That guard inferred user intent from responder state, which carries no meaning on a window AppKit just pre-filled.

Fix

Carry focus as an explicit one-shot intent instead of inferring it from responder state:

• QueryTabManager.addTab(claimFocus:) sets pendingFocusTabId (@ObservationIgnored, so it never triggers a render loop).
• Both new-tab paths opt in: in-place addTab and the new-window .newEmptyTab path. Restored tabs and table/content tabs do not, so they never steal focus.
• The view layer reads the flag for the matching tab, threads claimFocusOnAppear through QueryEditorView to SQLEditorView, and clears the flag in .onAppear (read-only in body).
• SQLEditorView calls coordinator.scheduleEditorFocusClaim(); prepareCoordinator then calls makeFirstResponder unconditionally when the latch is set, with an acceptsFirstResponder precheck. The old firstResponder == nil check stays only as the fallback for non-intent cases.

The native API (deferred makeFirstResponder, the only way to focus the CodeEditSourceEditor NSTextView, which is opaque to SwiftUI @FocusState) was already correct; only the gating changed.

Tests

• QueryTabManagerFocusTests (new): claimFocus sets/updates pendingFocusTabId; absent it stays nil; file-reopen dedup and addTableTab do not set it.
• SQLEditorCoordinatorTests (extended): the focus-claim latch starts false, scheduleEditorFocusClaim() flips it, idempotent.

The live makeFirstResponder path needs an NSWindow and a connection, so it is not headless-deterministic; it is verified by manual repro of both scenarios above. This matches the existing unit-only FilterFocusStateTests.

Notes

swiftlint lint --strict passes on the changed files.