migrate from yarn 1 to pnpm

- switch root package manager to pnpm 10.33.4 via packageManager field
- add .npmrc with node-linker=hoisted for RN/Expo compatibility
- convert yarn resolutions to pnpm.overrides; pin psl@1.9.0 and @types/psl@1.1.1
  to keep types resolving under exports-aware resolution
- pin react-compiler-runtime and babel-plugin-react-compiler to real rc.3 (the
  deprecated "Wrong version name was published" tag would otherwise resolve)
- add pnpm.onlyBuiltDependencies allowlist for @sentry/cli, core-js-pure,
  esbuild, unrs-resolver
- regenerate pnpm-lock.yaml; delete yarn.lock; drop postinstall-postinstall
- update all workflows, Dockerfile, Dockerfile.embedr (root-level), Makefile,
  conductor.json; bskyembed/bskylink/bskyogcard/dev-env stay on yarn
- update docs (CLAUDE.md, docs/build.md, docs/testing.md, docs/localization.md,
  bskyweb/README.md, scripts/push-notification/README.md, BlueskyClip/README.md)

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

scripts/push-notification/README.md

@@ -29,7 +29,7 @@ directly in Xcode.
 
 1. Boot an iOS simulator and install the app:
    ```
-   yarn ios
+   pnpm ios
    ```
 2. Sign in to the account you'll be testing against. The `recipientDid` in
    each payload is substituted at send time and must match the signed-in DID,