fix: corrected worktree baseline capture with synthetic tree diff

- Added untracked worktree baseline capture via `untrackedPatch` and synthetic tree diffing.
- Added fallback-aware backend ordering by collecting host candidates and retrying alternates on unavailable PAL.
- Hardened overlay mount lifecycle by removing stale overlays and deleting upper/work dirs after unmount.
- Refined ZFS clone deletion to validate ownership and remove dataset+origin only when checks pass.
- Updated ProjFS integration to use extended-info callbacks and symlink metadata reads.
- Updated rcopy path handling to absolutize paths, and added `writeTree` plus combined shell timeout checks.

packages/coding-agent/src/utils/git.ts

@@ -895,6 +895,11 @@ export async function readTree(
 	await runEffect(cwd, ["read-tree", treeish], options);
 }
 
+/** Write the current index as a tree and return its object id. */
+export async function writeTree(cwd: string, options: Pick<CommandOptions, "env" | "signal"> = {}): Promise<string> {
+	return (await runText(cwd, ["write-tree"], options)).trim();
+}
+
 // ════════════════════════════════════════════════════════════════════════════
 // API: show
 // ════════════════════════════════════════════════════════════════════════════