chore(task): archive 08-19-gaode-junction-reference

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.trellis/tasks/archive/2026-08/08-19-gaode-junction-reference/design.md

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+# Technical Design
+
+## Boundary
+
+The native compiler remains authoritative for OSM road identity, directed lanes,
+connections, traffic signals, stop lines, and preview routes. A reference layer is
+an optional geometry-calibration input consumed before junction surface publication.
+
+## Proposed Flow
+
+```text
+optional reference GeoJSON (GCJ-02)
+  -> validate schema and coordinate bounds
+  -> GCJ-02 to WGS84 conversion
+  -> associate reference footprint with an OSM junction node
+  -> classify geometry by observable shape, not opaque vendor type alone
+  -> derive bounded junction-shape parameters
+  -> native compiler creates surface/connectors as usual
+  -> diagnostics compare generated geometry with reference
+```
+
+The first production validation keeps the reference overlay/diagnostic, then enables a
+bounded `cross` junction template for explicitly configured references. Connector
+endpoints and movement enumeration still come from the native model. T and complex
+junctions remain on the existing algorithm until their templates are separately validated.
+
+## Input Contract
+
+Use an optional area-level reference configuration rather than a hard-coded filename.
+The sample points to `inputs/osm/珠山湖大道（枫树二路）口.geojson`, declares `GCJ-02`,
+and identifies the target through OSM node `8005332807` or a stable spatial/name match.
+The file is not assumed to contain a CRS member; the configured source CRS is required.
+
+## Geometry Safety
+
+- Convert all reference coordinates to WGS84 before distance/overlap tests.
+- Reject malformed or non-finite coordinates and references outside the OSM bounds plus a
+  bounded tolerance.
+- Never let a reference polygon create a movement, lane, signal, or stop-line record.
+- Keep a fallback path to the current `compileGeometry()` junction algorithm.
+
+## Compatibility And Rollback
+
+No-reference configs and existing output schemas remain unchanged. The experiment can be
+disabled by omitting the reference section or setting it disabled. Generated diagnostics
+must record source file hash, conversion mode, matched OSM node, and whether fallback was used.
+No source reference file is rewritten.
+
+## Open Technical Work
+
+1. Select the smallest reusable geometry parameter set from the sample (approach cutback,
+   corner radius/rounding, island/marking envelopes, and tolerances).
+2. Implement and test GCJ-02 conversion independently from compiler logic.
+3. Compare the sample against all native junctions near the converted footprint before any
+   production surface override is enabled.
+4. Add topology classification and template dispatch; only cross is enabled in this validation.
+5. Preserve native connectors and controls while replacing only the bounded junction surface geometry.