Task group 1 of planner-route-encoding. Framework-free `route-codec.ts`:
- encodePolyline/decodePolyline — fixed-precision (1e5) delta + zig-zag
varint + base64; lossless to ~1 m, version-tagged ("p1:").
- encodeRuns/decodeRuns — run-length codec for the per-coordinate
road-metadata channels, tagged ("r1:").
- isEncodedPolyline/isEncodedRuns — so the read path (group 3) tells the
new encoding apart from legacy JSON.
Not yet wired into route-data.ts (groups 2–3). Verified: map-core
typecheck + lint clean, 52/52 tests (round-trip within 1 m, empty/single,
RLE collapse, >3x smaller than JSON).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Follow-up to the planner WS reconnect-loop incident. Proposes compactly
encoding the computed route in the Yjs session doc (single-source geometry
+ delta/varint polyline + run-length-encoded road metadata, dual-format
backward-compatible reads) to cut a ~305 KB / 77 km route to ~40–60 KB —
WITHOUT changing the routing-host "compute once, share via Yjs" model or
GPX export output.
Artifacts: proposal, design, specs (new planner-route-encoding
capability), tasks. Validates --strict. Ready for /opsx:apply.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
