v2 tagged-section container (D-030): raw ISLA magic + u32 version gate,
[u32 tag][u64 length][payload] sections — params (resolved generation
inputs incl. impact centre), heights f32, biomes u8, towns with the
highway-node flag, four road tiers identified by tag not position.
- BlueprintFormat.cs: the single tag/constant registry.
- BlueprintWriter.WriteV2: blueprint-typed, callable outside a
generation run; generator and harness are both just callers.
- ExportMapData dual-writes: v2 under the primary seed name, legacy v1
beside it as _v1.dat (safety net; removal is a future task).
- MapDataParser: LoadMapDataFromPath entry point; v1 parse body
extracted intact as LoadV1 (v2 reader lands in the next commit).
- RoundTripHarness scene: load v1 -> write v2 -> load v2 -> semantic
equality, headless, seconds per cycle.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
