feat(perf): 增加大数据压测脚手架

docs/performance.md

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+# V2.6 Performance Harness
+
+V2.6 adds a deterministic large-data fixture and a small HTTP performance harness for the current hot paths. The goal is to make performance regressions visible before adding more background jobs and Xiaobao automation.
+
+## Fixture Sizes
+
+The fixture script creates only `perf-*` rows and can be rerun safely. It covers:
+
+- products
+- projects
+- versions
+- requirements
+- version plans
+- dev tasks
+- test cases
+- bugs
+- work activities
+- Xiaobao risk summaries
+
+Preset sizes:
+
+| Size | Purpose |
+| --- | --- |
+| `small` | Local smoke fixture. Fast dry-run and minimal database seed. |
+| `medium` | Default performance gate for V2.6 hot APIs. |
+| `large` | Stress fixture for query/index audit work. |
+
+Stable anchors used by the harness:
+
+```text
+productId=perf-product-001
+versionId=perf-version-001-001-001
+userId=perf-user-dev-01
+```
+
+## Commands
+
+Dry-run without database access:
+
+```bash
+node scripts/seed-large-dataset.mjs --size small --dry-run
+node scripts/perf-check.mjs --base-url http://localhost:3001/api/v1 --dry-run
+```
+
+Seed a database:
+
+```bash
+pnpm perf:seed -- --size small
+```
+
+Run the hot-path harness against a running NestJS API:
+
+```bash
+pnpm perf:check -- --base-url http://localhost:3001/api/v1
+```
+
+## Hot Probes
+
+`perf-check` measures p50 and p95 latency, records HTTP status code counts, and exits non-zero when a request fails or p95 exceeds the current query budget.
+
+| Probe | Endpoint | p95 Budget |
+| --- | --- | ---: |
+| Runtime version | `/health/version` | 500ms |
+| Requirement pool | `/v2.2/requirements?productId=perf-product-001&q=REQ&limit=50` | 1000ms |
+| Version detail | `/v2.2/versions/perf-version-001-001-001/detail-data` | 1500ms |
+| Workspace | `/v2.2/workspace?userId=perf-user-dev-01` | 1200ms |
+| Xiaobao warning | `/v2.2/xiaobao-warning?manager=true` | 1000ms |
+
+The medium fixture is the V2.6 acceptance target. Large fixture runs are for index audit and explain-plan work, not for every local commit.
+
+## Notes
+
+- `seed-large-dataset` uses deterministic IDs and dates so repeated runs are comparable.
+- Non-dry-run seeding deletes and recreates only `perf-*` rows.
+- The harness intentionally depends on public API endpoints instead of calling Prisma directly; it measures the same path the frontend uses.