GPUI: New Terminal startup is very slow on Windows

[maddada]

Environment

• GPUI app
• Windows

Problem

Starting a terminal with the New Terminal button has become very slow on Windows.

This is a performance regression in the GPUI app.

Expected behavior

A new terminal should start promptly after clicking New Terminal.

[maddada]

Applied fix in the working tree.

• Windows New Terminal now uses one local-only atomic gxserver operation instead of four serial RPCs and repeated provider probes.
• The operation transactionally allocates the durable session, starts zmx once, returns a direct require-existing attach command without a list probe, and preserves authoritative WSL cwd/Monaco context.
• Failure and cancellation paths compensate the exact provider/session and publish consistent presentation repairs.
• Concurrent allocation uses an immediate SQLite transaction; presentation revisions, snapshots, and per-client delivery are ordered.
• Event delivery is bounded and fails closed on queue overflow or broadcast lag so clients rehydrate from a fresh snapshot.
• macOS/Linux keep their existing creation lifecycle.

Final static verifier: PASS.

Per request, no tests, builds, app launch, commit, or push were performed.