Add area quality gate

.trellis/tasks/08-04-add-area-quality-gate/prd.md

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+# Add area quality gate
+
+## Goal
+
+Add a lightweight check:area command that turns diagnostics and manifests into pass/fail quality gates.
+
+## Requirements
+
+- Add a lightweight `check:area` npm command for an area quality gate.
+- The command must not run QGIS, Blender, Cesium, compression, or rebuild stages.
+- The command must reuse the same diagnostics source of truth used by
+  `diagnose:area`; avoid duplicating OSM parsing, artifact checks, GLB budget
+  checks, or manifest stale checks.
+- The first quality gate must fail on:
+  - invalid or missing OSM bounds
+  - malformed building multipolygon relations
+  - missing baseline GLB / metadata / Cesium preview artifacts
+  - invalid metadata JSON
+  - GLB size / node / image budgets exceeded
+  - missing, invalid, or stale expected stage manifests
+- Missing QGIS preview remains a warning in this first version.
+- The command must print a concise pass/fail report and use exit code `0` for
+  pass and `1` for fail.
+- README and pipeline spec must document command usage and failure policy.
+
+## Acceptance Criteria
+
+- [x] `npm run check:area -- --config config/areas/nantaizi-lake-innovation-valley.json`
+      passes against current nantaizi outputs.
+- [x] The check report includes pass/fail counts and any warning lines.
+- [x] `check:area` exits non-zero for a deliberately impossible missing-output
+      config or equivalent controlled failure case.
+- [x] `diagnose:area` still works after any shared diagnostics refactor.
+- [x] Syntax checks pass for changed Node scripts.
+- [x] README and Trellis pipeline spec document `check:area`.
+
+## Notes
+
+- Keep `prd.md` focused on requirements, constraints, and acceptance criteria.
+- Lightweight tasks can remain PRD-only.
+- For complex tasks, add `design.md` for technical design and `implement.md` for execution planning before `task.py start`.