chore(papi): commit the sources behind the four polkadot-api packages

papi-utils, bizinikiwi-bindings, metadata-builders and merkleize-metadata
held only dist/ builds, and no repository held their source. Every
source map in dist/ embeds the TypeScript it was compiled from; that is
now committed as src/ (59 files), and it matches upstream polkadot-api
(MIT) exactly once @polkadot-api/* imports are renamed:

  papi-utils           @polkadot-api/utils 0.2.0
  bizinikiwi-bindings  @polkadot-api/substrate-bindings 0.16.6
  metadata-builders    @polkadot-api/metadata-builders 0.13.0-0.13.2
  merkleize-metadata   @polkadot-api/merkleize-metadata 1.1.21-1.1.23

scripts/check-papi-sources.mjs, run in the lint job, fails unless the
source embedded in dist/ is exactly the committed src/. tsconfig.json
excludes these src/ trees; ESLint already skipped the packages. Each
README now states the upstream package and version.

.github/workflows/pr-any.yml

@@ -31,3 +31,8 @@ jobs:
     - name: check built manifests
       if: matrix.step == 'build'
       run: python3 scripts/check-built-manifests.py .
+    # The four polkadot-api packages ship committed dist/ builds; their source
+    # maps must embed exactly the src/ committed beside them.
+    - name: check papi sources
+      if: matrix.step == 'lint'
+      run: node scripts/check-papi-sources.mjs