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

ffi/zig/test/integration_test.zig

@@ -1,5 +1,5 @@
 // {{PROJECT}} Integration Tests
-// SPDX-License-Identifier: AGPL-3.0-or-later
+// SPDX-License-Identifier: PMPL-1.0-or-later
 //
 // These tests verify that the Zig FFI correctly implements the Idris2 ABI