fix(windows): suppress console popup on child_process calls (#498)

On Windows, v0.9.5's detached shared daemon (#411) has no inherited console,
so any console-subsystem child it spawns gets a fresh visible console window
unless the spawn passes `windowsHide: true`. The fix adds the flag to all
ten `spawnSync` / `execFileSync` / `execSync` call sites across extraction,
sync, installer, and the WASM-flags relaunch. macOS/Linux ignore the option,
so this is a no-op elsewhere.

Fixes #485, #510, #530.

Co-authored work:
- #498 (csw-chen) — full sweep across extraction, sync, installer, and wasm-runtime. **This is the change being merged.**
- #505 (yushengruohui) — independently identified and fixed the 7 git execFileSync sites. Superseded by #498's broader sweep; same diagnosis.
- #521 (JirA44) — independently identified and fixed the WASM-runtime spawnSync re-exec. Superseded by #498's broader sweep; same diagnosis.

Validated on Windows 11 ARM64 (Parallels): a detached parent's 15 git spawns produce 15 visible black flash-windows without the fix and 0 with it.

src/mcp/engine.ts

@@ -147,8 +147,7 @@ export class MCPEngine {
 
     const resolvedRoot = findNearestCodeGraphRoot(searchFrom);
     if (!resolvedRoot) {
-      // No .codegraph/ above searchFrom — that's not an error, sessions may
-      // still discover one later via roots/list.
+      // No .codegraph/ above searchFrom. Sessions may still discover one later via roots/list
       this.projectPath = searchFrom;
       return;
     }