chore: update agent skills and project config

- add vercel-react-best-practices skill (SKILL.md + full-guide.md)
- slim CLAUDE.md to import shared AGENTS.md conventions
- promote go-ntlmssp to a direct dependency in go.mod

.agents/skills/vercel-react-best-practices/SKILL.md

@@ -0,0 +1,31 @@
+---
+name: vercel-react-best-practices
+description: React and Next.js performance optimization guidelines from Vercel Engineering. Use when writing, reviewing, or refactoring React/Next.js code involving components, Next.js pages, Server Components, Server Actions, data fetching, bundle size, rendering behavior, or performance improvements.
+---
+
+# Vercel React Best Practices
+
+Use this skill for React and Next.js performance work. The full Vercel guide is stored in `references/full-guide.md`; do not read the whole file by default.
+
+## Workflow
+
+1. Identify the relevant performance area from the task or code under review.
+2. Search `references/full-guide.md` for the matching section or rule heading.
+3. Read only the relevant section before changing or reviewing code.
+4. Prioritize higher-impact categories before lower-impact micro-optimizations.
+
+## Priority Order
+
+1. Eliminating waterfalls: sequential async work, API route chains, missing `Promise.all`, Suspense boundaries.
+2. Bundle size optimization: barrel imports, heavy client modules, dynamic imports, deferred third-party libraries.
+3. Server-side performance: Server Actions auth, RSC serialization, per-request deduplication, cross-request caching, `after()`.
+4. Client-side data fetching: SWR deduplication, global listeners, passive scroll listeners, localStorage schema.
+5. Re-render optimization: derived state, effect dependencies, memo boundaries, functional state updates, transitions, refs.
+6. Rendering performance: hydration mismatches, long lists, static JSX, SVG precision, resource hints, script loading.
+7. JavaScript performance: repeated lookups, array passes, storage reads, layout thrashing, sort/min-max choices.
+8. Advanced patterns: one-time initialization, stable callback refs, effect events.
+
+## Reference
+
+- Full compiled guide: `references/full-guide.md`
+- Original project: https://github.com/vercel-labs/agent-skills/tree/main/skills/react-best-practices