feat(rebuild): #56 human rebuild errors point at doctor

sys-update / sys-rebuild / home-update tee output and on failure print
the last 40 log lines plus nomarchy-doctor + RECOVERY.md. theme-sync HM
switch failure notify/die text matches. Close #56.

Verified: V1 (HM rebuild; failure-footer shell smoke).

pkgs/nomarchy-theme-sync/nomarchy-theme-sync.py

@@ -361,8 +361,15 @@ def run_switch() -> None:
     notify("Applying changes — rebuilding the desktop…", persistent=True)
     result = subprocess.run(argv)  # stream output to the caller's terminal
     if result.returncode != 0:
-        notify("Rebuild FAILED — see terminal / journal", urgency="critical")
-        die("rebuild failed (state file already updated; fix and re-run)")
+        # BACKLOG #56: point at doctor, not a silent wall of Nix noise.
+        notify(
+            "Rebuild FAILED — scroll up for last lines; run nomarchy-doctor",
+            urgency="critical",
+        )
+        die(
+            "rebuild failed (state already written; fix and re-run). "
+            "Diagnose: nomarchy-doctor. Recovery: docs/RECOVERY.md"
+        )
     notify("Changes applied ✓")
     # Waybar runs from Hyprland's exec-once (not a systemd unit HM would
     # restart on switch), so nudge the running bar onto the freshly rebuilt