fix(shim): use SPDX LicenseRef syntax for PMPL so JSR accepts the license

JSR validates the `license` field in `deno.json` against the SPDX
license list and rejects unknown identifiers:

    Failed to publish @hyperpolymath/affinescript at 0.1.2:
      The license specified in the "license" field of your
      configuration file, or in the LICENSE file was not recognized.

`PMPL-1.0-or-later` is not on the SPDX list (it's the custom Polymath
Public License from this repo).  The SPDX-sanctioned way to declare a
custom license is the `LicenseRef-*` prefix, which JSR accepts.

Switch `packages/affinescript-cli/deno.json` to
`LicenseRef-PMPL-1.0-or-later`.  No behaviour change; the licence the
package is offered under is exactly the same.  The repo's `LICENSE`
file is the canonical text.

Dry-run is clean post-change (4 files, no warnings).  This is the last
blocker for the v0.1.2 JSR publish — package exists, OIDC trusted
publisher is wired, types are typed; license string was the final gate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

packages/affinescript-cli/deno.json

@@ -4,7 +4,7 @@
   "exports": {
     ".": "./mod.js"
   },
-  "license": "PMPL-1.0-or-later",
+  "license": "LicenseRef-PMPL-1.0-or-later",
   "publish": {
     "exclude": ["mod_test.js"]
   },