fix(FN-2897): harden npm bundle packaging and merge recovery flows

- Strip private @fusion/* workspace devDependencies from the published CLI manifest via prepare-publish-manifest and package metadata updates
- Replace cross-spawn usage and add staged bundle layout assertions to verify resolver output in dist packaging
- Add per-task/project model override resolution across core, dashboard settings/task modals, and route coverage with new regression tests
- Strengthen engine merge/recovery handling for paused/interrupted/squash paths and surface merger timeline activity with additional self-healing and merger tests
- Add changesets for npm bundle dependency fixes, project model override stabilization, and FTS5 corruption recovery

Fusion-Task-Id: FN-2897

packages/cli/scripts/prepare-publish-manifest.mjs

@@ -0,0 +1,42 @@
+/* global process, URL, console */
+
+import { existsSync, readFileSync, writeFileSync, unlinkSync } from "node:fs";
+
+const mode = process.argv[2];
+const packageJsonPath = new URL("../package.json", import.meta.url);
+const backupPath = new URL("../package.json.pack-backup", import.meta.url);
+
+if (mode === "prepack") {
+  if (existsSync(backupPath)) {
+    // Clean up stale backup from interrupted runs.
+    unlinkSync(backupPath);
+  }
+
+  const original = readFileSync(packageJsonPath, "utf8");
+  writeFileSync(backupPath, original, "utf8");
+
+  const pkg = JSON.parse(original);
+  const devDependencies = { ...(pkg.devDependencies || {}) };
+  delete devDependencies["@fusion/core"];
+  delete devDependencies["@fusion/dashboard"];
+  delete devDependencies["@fusion/engine"];
+  delete devDependencies["@fusion/pi-claude-cli"];
+
+  pkg.devDependencies = devDependencies;
+  writeFileSync(packageJsonPath, `${JSON.stringify(pkg, null, 2)}\n`, "utf8");
+  process.exit(0);
+}
+
+if (mode === "postpack") {
+  if (!existsSync(backupPath)) {
+    process.exit(0);
+  }
+
+  const backup = readFileSync(backupPath, "utf8");
+  writeFileSync(packageJsonPath, backup, "utf8");
+  unlinkSync(backupPath);
+  process.exit(0);
+}
+
+console.error("Usage: node ./scripts/prepare-publish-manifest.mjs <prepack|postpack>");
+process.exit(1);