Fix SPDX headers: AGPL-3.0-or-later → PMPL-1.0-or-later

Replace legacy AGPL-3.0-or-later SPDX identifiers with the correct
PMPL-1.0-or-later (Palimpsest License) across justfiles, Mustfiles,
shell scripts, config files, dotfiles, and source code.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

Mustfile

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-License-Identifier: PMPL-1.0-or-later
 # Mustfile - hyperpolymath mandatory checks
 # See: https://github.com/hyperpolymath/mustfile
 

flake.nix

@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-License-Identifier: PMPL-1.0-or-later
 # SPDX-FileCopyrightText: 2025 Jonathan D.A. Jewell
 # flake.nix — robot-vacuum-cleaner (Nix fallback, Guix is primary)
 {