fix(server): restore Windows terminal startup after node-pty upgrade

[SegFaultZero]

What Changed

Wait for a valid Windows terminal PID before completing the node-pty adapter's spawn operation. This restores terminal startup after the node-pty upgrade; the terminal manager keeps storing the PID once, and Unix startup is unchanged.

The adapter uses node-pty's private ready_datapipe event, validates the PID, and removes listeners on completion or interruption. Startup failures are reported as PtySpawnError. Cancellation uses the internal Windows agent because public kill() waits for first output. Comments link the upstream changes that require these compatibility hooks.

Why

Terminals on Windows are broken after the node-pty upgrade: opening a terminal displays "[terminal] The environment request failed." instead of a usable shell.

After pingdotgg#13748 upgraded node-pty from 1.1.0 to 1.2.0-beta.15, Windows spawn initially returns PID 0 while process creation is still pending. T3 immediately stored that startup value and never refreshed it when node-pty assigned the real PID. Clients rejected the resulting terminal snapshots because the contract accepts only a positive PID or null, displaying "[terminal] The environment request failed."

microsoft/node-pty#885 deferred Windows process creation to avoid blocking on named pipes. Waiting for its internal readiness event handles silent processes without polling or waiting for shell output. The private API dependency is confined to the adapter.

Validation

• 97 focused tests passed: vp test run src/terminal/NodePtyAdapter.test.ts src/terminal/Manager.test.ts from apps/server.
• Server typecheck and targeted lint passed.
• vp run build:desktop succeeded on Windows.
• Native Windows PTY check returned a positive PID and preserved output and exit delivery.
• Reporter ran the compiled desktop app and confirmed that terminals work.

Implemented with GPT-6-Astra through the Codex harness.

[SegFaultZero]

looks good