pkgmgr-wrapper: improve Nix detection and auto-initialization

- Extend PATH probing to include /home/nix/.nix-profile/bin/nix (container mode).
- Automatically invoke init-nix.sh when nix is not found before first run.
- Ensure pkgmgr always attempts a one-time Nix initialization instead of failing prematurely.
- Improve error message to clarify that nix was still missing *after* initialization attempt.
- Keep existing flake-based execution path unchanged (exec nix run …).

This makes the wrapper fully reliable across Debian/Ubuntu package installs,
fresh containers, and minimal systems where Nix is not yet initialized.

https://chatgpt.com/share/693b005d-b250-800f-8830-ab71685f51b3

scripts/pkgmgr-wrapper.sh

@@ -8,19 +8,18 @@ fi
 
 FLAKE_DIR="/usr/lib/package-manager"
 
-# ------------------------------------------------------------
-# Try to ensure that "nix" is on PATH
-# ------------------------------------------------------------
+# ---------------------------------------------------------------------------
+# Try to ensure that "nix" is on PATH (common locations + container user)
+# ---------------------------------------------------------------------------
 if ! command -v nix >/dev/null 2>&1; then
-  # Common locations for Nix installations
   CANDIDATES=(
     "/nix/var/nix/profiles/default/bin/nix"
     "${HOME:-/root}/.nix-profile/bin/nix"
+    "/home/nix/.nix-profile/bin/nix"
   )
 
   for candidate in "${CANDIDATES[@]}"; do
     if [[ -x "$candidate" ]]; then
-      # Prepend the directory of the candidate to PATH
       PATH="$(dirname "$candidate"):${PATH}"
       export PATH
       break
@@ -28,13 +27,22 @@ if ! command -v nix >/dev/null 2>&1; then
   done
 fi
 
-# ------------------------------------------------------------
-# Primary (and only) path: use Nix flake if available
-# ------------------------------------------------------------
+# ---------------------------------------------------------------------------
+# If nix is still missing, try to run init-nix.sh once
+# ---------------------------------------------------------------------------
+if ! command -v nix >/dev/null 2>&1; then
+  if [[ -x "${FLAKE_DIR}/init-nix.sh" ]]; then
+    "${FLAKE_DIR}/init-nix.sh" || true
+  fi
+fi
+
+# ---------------------------------------------------------------------------
+# Primary path: use Nix flake if available
+# ---------------------------------------------------------------------------
 if command -v nix >/dev/null 2>&1; then
   exec nix run "${FLAKE_DIR}#pkgmgr" -- "$@"
 fi
 
-echo "[pkgmgr-wrapper] ERROR: 'nix' binary not found on PATH."
+echo "[pkgmgr-wrapper] ERROR: 'nix' binary not found on PATH after init."
 echo "[pkgmgr-wrapper] Nix is required to run pkgmgr (no Python fallback)."
 exit 1