chore: switch package manager to bun and create docs for codebase

Makefile

@@ -10,20 +10,20 @@ generate:
 	curl -fsSL $(SPEC_URL) -o $(SPEC_PATH)
 	@echo "Generating TypeScript types..."
 	mkdir -p src/models
-	pnpm generate
+	bun run generate
 
 lint:
-	pnpm exec biome check .
+	bunx biome check .
 
 test:
-	pnpm vitest run --exclude tests/integration
+	bunx vitest run --exclude tests/integration
 
 test-integration:
-	pnpm test:integration
+	bun run test:integration
 
 check:
 	$(MAKE) lint
 	$(MAKE) test
 
 build:
-	pnpm build
+	bun run build