set up claude pr auto-review

adds auto-review and migrates the existing @claude mention workflow to
the org-wide reusable workflows in bluesky-social/.github, matching
tango. adds a social-app-specific review prompt covering platform
parity, ALF/Lingui conventions, React Compiler, and the design system.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/claude-review.yml

@@ -0,0 +1,24 @@
+name: claude-review
+
+# Thin caller for the org-wide reusable review workflow in
+# bluesky-social/.github. See .github/claude-review-prompt.md for
+# social-app-specific prompt content.
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+
+# Reusable workflows can only use permissions granted by the caller.
+# Default repo setting is read-only; this caller explicitly opts in to
+# the writes the reusable workflow needs (comment on PRs, get OIDC token).
+permissions:
+  contents: read
+  pull-requests: write
+  id-token: write
+
+jobs:
+  review:
+    uses: bluesky-social/.github/.github/workflows/claude-review.yml@v1
+    secrets: inherit
+    with:
+      prompt-file: .github/claude-review-prompt.md