fix(desktop): stage @fusion/core PG migrations into packaged builds

Bare tsc never copies .sql files into core's dist, and the desktop staging
had no equivalent of the CLI's tsup migrations hook, so every packaged
desktop build shipped without dist/postgres/migrations and Local mode
crashed schema init (ENOENT 0000_initial.sql) after embedded Postgres
started. buildCore() now stages the migrations beside the compiled output,
stageDesktopDeploy() re-stages them into the deployed closure, and
verifyCoreMigrationsStaged() fails the build if the baseline migration is
missing from the stage.

Verified end to end: packed mac-arm64 app boots with isolated home,
embedded PG 15.18 initializes from packaged migrations, /api/health 200.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/desktop/scripts/workspace-tools.ts

@@ -42,8 +42,29 @@ export function runWorkspaceBin(command: string, args: string[], cwd: string): P
   });
 }
 
+/*
+ * FNXC:DesktopPostgresMigrations 2026-07-17-18:20:
+ * @fusion/core's build is bare tsc, which never copies the PostgreSQL migration
+ * .sql files into dist — core's schema-applier resolves them from
+ * dist/postgres/migrations at runtime (join(__dirname, "migrations", ...)).
+ * The CLI compensates in packages/cli/tsup.config.ts, but the desktop had no
+ * equivalent, so every packaged desktop build shipped without migrations and
+ * Local mode crashed schema init with ENOENT for 0000_initial.sql after the
+ * embedded Postgres started. Stage the migrations beside the compiled output
+ * whenever the desktop builds core so both dev and the pnpm-deploy staged
+ * closure (core's files field packs dist/**) contain them.
+ */
+const coreMigrationsSrcDir = resolve(workspaceRoot, "packages", "core", "src", "postgres", "migrations");
+
+async function stageCoreMigrations(coreDistDir: string): Promise<void> {
+  const dest = resolve(coreDistDir, "postgres", "migrations");
+  await rm(dest, { recursive: true, force: true });
+  await cp(coreMigrationsSrcDir, dest, { recursive: true });
+}
+
 export async function buildCore(): Promise<void> {
   await runWorkspaceBin("tsc", [], resolve(workspaceRoot, "packages", "core"));
+  await stageCoreMigrations(resolve(workspaceRoot, "packages", "core", "dist"));
 }
 
 // FNXC:DesktopBuild 2026-07-01-19:45:
@@ -240,10 +261,34 @@ export async function stageDesktopDeploy(): Promise<void> {
     ? config.replace(/output:\s*dist-electron/, "output: ../dist-electron")
     : `directories:\n  output: ../dist-electron\n${config}`;
   await writeFile(stagedConfig, patched);
+
+  /*
+   * FNXC:DesktopPostgresMigrations 2026-07-17-18:20:
+   * pnpm deploy copies whatever is in core's dist at stage time. If core was
+   * last built by a bare `tsc` outside this package's scripts (e.g. root
+   * `pnpm build`), dist may lack the migration .sql files even though buildCore()
+   * above stages them. Re-stage them directly into the deployed closure
+   * (idempotent) and fail fast if the baseline migration is still missing, so a
+   * packaged app can never ship unable to initialize its embedded database.
+   */
+  await stageCoreMigrations(resolve(desktopDeployDir, "node_modules", "@fusion", "core", "dist"));
+  await verifyCoreMigrationsStaged();
   await verifyEmbeddedPostgresPayloads();
   console.log(`[desktop:build] Deploy staged at ${desktopDeployDir}`);
 }
 
+export async function verifyCoreMigrationsStaged(deployDir = desktopDeployDir): Promise<void> {
+  const baseline = resolve(deployDir, "node_modules", "@fusion", "core", "dist", "postgres", "migrations", "0000_initial.sql");
+  try {
+    await stat(baseline);
+  } catch {
+    throw new Error(
+      `Desktop staged closure is missing @fusion/core PostgreSQL migrations (${baseline}). ` +
+        "Packaged Local mode cannot initialize its embedded database without them.",
+    );
+  }
+}
+
 export async function buildDashboardClient(): Promise<void> {
   // FNXC:DesktopBuild 2026-07-13-12:15:
   // Clean the dashboard client output directory before building. Vite generates