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>

bskyweb/README.md

@@ -10,13 +10,13 @@ like:
 # install nodejs
 nvm install
 nvm use
-npm install --global yarn
+npm install --global pnpm
 
 # setup tools and deps (in top level of this repo)
-yarn install --frozen-lockfile
+pnpm install --frozen-lockfile
 
-# run yarn web dev server, if you wanted
-yarn web
+# run pnpm web dev server, if you wanted
+pnpm web
 ```
 
 Then build and copy over the big 'ol `bundle.web.js` file:
@@ -24,7 +24,7 @@ Then build and copy over the big 'ol `bundle.web.js` file:
 
 ```bash
 # in the top level of this repo
-yarn build-web
+pnpm build-web
 ```
 
 ### Golang Daemon