feat: move validate skill to opencode and remove Langfuse dependency

- Move SKILL.md and batch_validate.py from packages/altimate-code/src/skills/validate/ to packages/opencode/src/skill/validate/
- Rewrite batch_validate.py to call Altimate backend API directly via SSE for single trace, date range, and session modes; remove all Langfuse usage
- Fix build.ts and validate.ts to reference new skill path (src/skill/validate/)
- Auto-install validate skill after bun run build via postbuild step in packages/opencode/package.json
- Remove empty packages/altimate-code/src/hooks/settings.json

Author: Bharatram-altimate-ai

bun.lock

@@ -8,7 +8,7 @@
   "scripts": {
     "typecheck": "tsgo --noEmit",
     "test": "bun test --timeout 30000",
-    "build": "bun run script/build.ts",
+    "build": "bun run script/build.ts && ./bin/altimate-code validate install",
     "dev": "bun run --conditions=browser ./src/index.ts",
     "db": "bun drizzle-kit"
   },