coord(M03): claim M2 placement grouper

coordination/claims/M03-RND-M2-PLACEMENT-GROUPER-001.md

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+# M03-RND-M2-PLACEMENT-GROUPER-001 — M2 placement grouper
+
+<!-- OPENWC_CLAIM:M03-RND-M2-PLACEMENT-GROUPER-001:sindo-main-codex:2026-07-19 -->
+
+## Ownership
+
+- Target: M03
+- Program: RND
+- Owner/Agent ID: sindo-main-codex
+- Branch: `work/sindo-main-codex/m03-m2-placement-grouper`
+- Lease expires UTC: 2026-07-19
+- Integrator: M03 milestone integrator
+
+## Outcome
+
+Extract pure ADT M2 placement validation, path normalization and local-transform
+grouping from the worker callback into a scene-free service.
+
+## Non-goals
+
+- Change placement ordering, coordinate conversion, transform formulas or clamps.
+- Move WorkerThreadPool tasks, mutex/result queues, tile state or retry behavior.
+- Move build jobs, animation/mesh loading, caches, Nodes, MultiMesh or RIDs.
+- Generalize grouping policy, change batching or add a dependency.
+- Claim build-12340 placement or visual parity beyond preserved formulas.
+
+## Paths
+
+- Exclusive: `src/render/m2/m2_placement_grouper.gd`,
+  `src/tools/verify_m2_placement_grouper.gd`,
+  `docs/modules/m2-placement-grouper.md`, this claim
+- Shared/hotspots: `src/scenes/streaming/streaming_world_loader.gd`,
+  `docs/modules/m2-placement-transform-resolver.md`,
+  `docs/modules/world-renderer.md`, `docs/modules/README.md`, `RENDER.md`,
+  `targets/03-renderer-facade.md`
+- Generated/ignored: `.godot`, native DLL, generated ADT resources, caches and
+  proprietary renderer corpus
+
+## Contracts and data
+
+- Input: tile-local origin, MMDX name table and raw ADT M2 placement array
+- Output: fresh Dictionary keyed by historically normalized relative M2 path;
+  each value is a fresh ordered Array of tile-local `Transform3D` values
+- Invalid variants, out-of-range name IDs and empty paths are skipped
+- Backslashes become slashes; lowercase `.mdx/.mdl` suffixes become `.m2`
+- Transform basis/origin delegates to `M2PlacementTransformResolver`; final basis
+  scale retains the grouping-path clamp `max(scale, 0.0001)`
+- Cache/schema/coordinate versions: unchanged
+
+## Dependencies
+
+- Requires: current master `c34e538`, `M2PlacementTransformResolver`
+- Blocks: broader M2 worker/build decomposition
+- External state: none; tests use synthetic names and placement dictionaries
+
+## Verification
+
+- Commands: dedicated invalid/name/path/group-order/default/transform/scale and
+  bounded timing verifier; loader source boundary; resolver/registry/dedupe plus
+  facade/internal-access/manifest/shutdown/documentation/coordination gates
+- Fidelity evidence: exact loop rules and transform composition moved unchanged
+- Performance budget: linear over placement count with fresh output containers;
+  no Node, Resource, RID, task, mutex, cache or file access
+
+## Documentation deliverables
+
+- Inline grouper API documentation
+- New module spec with inputs/outputs, data-flow, lifecycle, ownership, failure,
+  performance, fidelity limitations and source map
+- Transform resolver, renderer/module registry and `RENDER.md` updates
+
+## Simplicity and naming
+
+- Important name: `M2PlacementGrouper`
+- Simplest solution: one stateless `group_placements` query
+- Rejected complexity: group/result classes, strategy interfaces, callbacks,
+  Resources, policies or generic spatial batching framework
+- Unavoidable complexity: raw ADT dictionaries remain at the parser adapter
+- Measured optimization evidence: bounded synthetic grouping loop
+
+## Status
+
+- State: claimed
+- Done: boundary, exact preservation rules and ownership published
+- Next: implement grouper, migrate worker callback, tests and docs
+- Blocked by:
+
+## Handoff
+
+- Commit:
+- Results:
+- Remaining risks:
+- Documentation updated: