* feat(#1933): VS Code IDE reference host binding — completes Phase 5 IDE profile
The reference VS Code host binding composes the Phase-3 engine seams for the
ide profile (host-integration.cts PROFILE_BASELINES): active model via vscode.lm
(createModelAdapter active + sendRequest), engine-owned hook bus
(createHookBus engine — VS Code has no host bus), sandboxed-storage stateIO
(createStateIO sandboxed-storage + host backend — no fs / no child_process),
and the imperative adapter (engine-as-library). Command surface: palette/chat.
VS Code is extension-distributed (Marketplace), not file-projected onto a config
dir, so it intentionally has NO runtime descriptor / --vscode installer entry —
the extension IS the host (architecturally N/A for the descriptor/installer
model, not a deferral). Mock-friendly binding (vscode.lm + hostStorage injected)
so it is behaviorally testable without a live VS Code host.
Tests: IDE profileOf classification; full seam composition (active model routes
to vscode.lm; engine bus pub/sub; sandboxed state routes to backend; imperative
adapter; command surface); fail-closed construction.
* fix(#1933): correct vscode fail-closed test case matrix
