chore(deps): upgrade pnpm to 11.18.0 (#132)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

pnpm-workspace.yaml

@@ -1,5 +1,11 @@
 packages:
   - "packages/*"
+# Dependency pins. pnpm 11 reads overrides ONLY from here — the package.json
+# "pnpm.overrides" block it used to honour is silently ignored, which resolved a second
+# copy of each of these.
+overrides:
+  "@anthropic-ai/sdk": "^0.91.1"
+  esbuild: "^0.28.1"
 injectWorkspacePackages: true
 syncInjectedDepsAfterScripts:
   - build