fnd(M01): add canonical coordinate mapper

Work-Package: M01-FND-COORDS-001
Agent: sindo-main-codex
Tests: coordinate mapper, M00 coordinate calibration, baseline manifest, coordination and documentation gates passed
Fidelity: five build 12340 camera points map within 0.002 yard; no visual parity claim

docs/adr/0001-canonical-world-coordinates.md

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+# ADR 0001: Canonical world coordinate contract
+
+- Status: Accepted for M01 contract implementation
+- Date: 2026-07-13
+- Work package: `M01-FND-COORDS-001`
+- Decision owners: M01 foundation/integration owners
+
+## Context
+
+OpenWC currently performs coordinate conversion in native ADT/WDT loaders,
+`StreamingWorldLoader`, sky, player and renderer diagnostic scripts. The same
+numbers are frequently carried in `Vector3` or dictionaries, so the coordinate
+space is implicit. Existing names also mix ADT filename indices, renderer X/Z
+indices and MDDF/MODF placement fields.
+
+M00 recorded five positions observed in WoW 3.3.5a build 12340. They verify the
+current client-position to Godot-position arithmetic within `0.002` yard, but
+they do not define a cross-layer contract and do not prove camera composition
+or visual parity.
+
+Independent references agree on a 64 by 64 ADT grid and an approximately
+`533.3333` yard tile size. They do not all use the word “canonical” for the same
+axis order. OpenWC therefore needs names tied to observable formats instead of
+adopting an internal convention from one reference project.
+
+## Decision
+
+### Canonical position
+
+`CanonicalWowWorldPosition(X, Y, Z)` preserves the numeric X/Y/Z order used by
+the WoW client, movement protocol and TrinityCore/AzerothCore world positions.
+X and Y are horizontal; Z is height. Units are WoW yards.
+
+`ServerWorldPosition` is a distinct type but converts component-for-component
+to canonical. The type boundary prevents a server record from being passed
+directly to renderer code and leaves room for adapter validation without a
+silent axis swap.
+
+### World extent and ADT indices
+
+The contract uses:
+
+```text
+ADT_TILE_SIZE_YARDS = 1600 / 3
+ADT_TILES_PER_MAP_AXIS = 64
+WOW_WORLD_HALF_EXTENT_YARDS = 32 * ADT_TILE_SIZE_YARDS
+
+tileX = floor(32 - canonical.X / ADT_TILE_SIZE_YARDS)
+tileY = floor(32 - canonical.Y / ADT_TILE_SIZE_YARDS)
+```
+
+`AdtTileCoordinate(tile_x, tile_y)` always means the indices in
+`Map_tileX_tileY.adt`. Results are intentionally not clamped: the exact
+south-east extent produces index 64 and remains diagnosable as out of bounds.
+Normal valid indices are 0 through 63.
+
+An `AdtTileLocalPosition` is measured east and south from the tile's
+north-west corner. An `AdtChunkCoordinate` uses `chunk_x` south and `chunk_y`
+east, with valid indices 0 through 15. These direction names avoid pretending
+that ADT file axes are Godot X/Z axes.
+
+### ADT placement fields
+
+MDDF/MODF position fields are represented in on-disk X/height/Z order:
+
+```text
+adt.X      = halfExtent - canonical.X
+adt.height = canonical.Z
+adt.Z      = halfExtent - canonical.Y
+```
+
+Model-local MDDF/MODF Euler corrections are not world orientation. They remain
+outside this contract until a placement-orientation package has format- and
+model-specific fixtures.
+
+### Godot renderer basis
+
+The compatibility renderer keeps one Godot unit equal to one WoW yard and uses
+Y-up coordinates from the north-west map extent:
+
+```text
+godot.X = halfExtent - canonical.Y  # east
+godot.Y = canonical.Z               # up
+godot.Z = halfExtent - canonical.X  # south
+```
+
+`GodotWorldPosition` contains scalars rather than `Vector3`. A scene/render
+adapter may construct `Vector3` only at its boundary.
+
+### World yaw
+
+Server/canonical yaw zero faces increasing WoW X; positive yaw turns toward
+increasing WoW Y. In the mapped Godot basis, Godot forward `-Z` and positive
+Y-axis yaw produce the same numeric world angle. Mapper conversions therefore
+normalize the value to `[-PI, PI)` without adding an offset.
+
+This identity applies to world-facing yaw only. It does not apply to M2/WMO
+asset axes or placement Euler triples.
+
+## Alternatives considered
+
+### Make renderer coordinates canonical
+
+Rejected because protocol, database and ADT adapters would silently inherit a
+presentation-specific offset and Y-up basis.
+
+### Adopt WoWee's internal canonical axis names unchanged
+
+Rejected because that reference swaps server X/Y into its chosen north/west
+ordering. OpenWC preserves observable client/server field names and makes the
+render/ADT transformations explicit instead.
+
+### Use `Vector3` plus comments
+
+Rejected because comments cannot prevent server, ADT and Godot values from
+being passed across the wrong boundary.
+
+### Generic vector-space or matrix framework
+
+Rejected as unnecessary complexity for fixed affine transforms and integer
+grid ownership rules.
+
+## Consequences
+
+- Network and server-data adapters can expose typed positions without knowing
+  Godot.
+- Renderer consumers must explicitly map and then create Godot vectors at their
+  own boundary.
+- ADT filename indices can no longer be confused with renderer X/Z tile names.
+- Existing native/parser and renderer conversions remain unchanged until
+  separate consumer migration packages merge after this contract.
+- Manual axis conversions become review/test violations once migration is
+  complete; this ADR alone does not delete compatibility paths.
+- Persisted schemas are unchanged. Future serialized positions must include an
+  explicit coordinate-space/version discriminator.
+
+## Verification
+
+- Five M00 build-12340 client camera positions map to the recorded Godot
+  checkpoints within `0.002` yard.
+- Server, ADT placement, Godot and tile-local conversions round-trip.
+- Exact center, tile, chunk and world-extent boundaries have explicit tests.
+- World-yaw normalization and round-trip cases cover cardinal angles and wrap.
+
+## References
+
+- [TrinityCore GridDefines](https://github.com/TrinityCore/TrinityCore/blob/master/src/server/game/Grids/GridDefines.h)
+- `reference/open-realm/games/world-of-warcraft/renderer/wow/r_wowmap_adt.c`
+- `reference/open-realm/games/world-of-warcraft/renderer/wow/r_wowmap_objects.c`
+- `reference/WoWee/include/core/coordinates.hpp`
+- [`../M00_FINAL_PAIRED_EVIDENCE.md`](../M00_FINAL_PAIRED_EVIDENCE.md)