chore: switch yarn from PnP to node-modules linker (#469)

Yarn 4 defaults to PnP (Plug'n'Play) which breaks TypeScript module
resolution for dependencies like @grpc/grpc-js, uuid, and @types/node.
Add .yarnrc.yml with nodeLinker: node-modules and ignore PnP artifacts.

Co-authored-by: William Chong <william-chong@outlook.com>

Author: github-actions[bot]

.gitignore

@@ -13,6 +13,13 @@ lerna-debug.log*
 !.yarn/sdks
 !.yarn/versions
 
+.pnp.*
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+
+
 # Diagnostic reports (https://nodejs.org/api/report.html)
 report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
 

.yarnrc.yml

@@ -0,0 +1 @@
+nodeLinker: node-modules