Module types/committed-data

The committedData mesh stamp — typed accessors for the memoized-concat no-op contract — plus its sibling elementIdMap stamp.

The progressive loaders MEMOIZE their LOD concatenation: an update whose view state is unchanged and that loaded no new LODs returns the SAME object reference as the previous update. The commit pipeline stamps that reference onto the mesh (mesh.userData.committedData) whenever geometry actually reaches the GPU, so a handler seeing getCommittedData(mesh) === data knows the GPU already holds this exact data and can skip the expensive process (nD→3D projection) and upload steps entirely.

The stamp is load-bearing in BOTH directions:

• PRESENCE + identity is the no-op fast-path key (above).
• ABSENCE signals LOD demotion: the demoted level's geometry returned to the evictable pool (and may since belong to another node), so consumers like the depth-sort coordinator treat a missing stamp as "this mesh's geometry no longer holds the commit's data". Presence therefore tests !== undefined, and clearing DELETES the property (never assigns undefined) — the stamp would otherwise keep the loader-returned source arrays reachable. (For Mesh this is no longer the ONLY such reference: rendering/mesh-geometry.ts's own currency stamps — meshColorsSource / meshNormalSource / meshAScalarSource — also pin the last committed colour/normal/scalar arrays on the geometry's userData, independent of this stamp.)

The elementIdMap sibling stamp. Picking needs to translate the STORAGE SLOT its shaders report (a position in the buffer now on the GPU) into the ON-DISK element index the per-element label CSR is keyed by. That map is a property of the committed buffers, not of any loader payload, so it lives here as a second mesh-level stamp rather than riding on the data object — a loaded payload can be a SliceCache-owned snapshot whose byte size was measured at store time, and commit-time mutation of it would both falsify that accounting and break the cache's never-mutated invariant. Contract:

• indexed by STORAGE slot; the value is the on-disk element index,
• written in LOCKSTEP with committedData so it always describes the buffers currently on the GPU (and cleared with it whenever those buffers are actually released — see clearCommittedData vs invalidateCommittedDataStamp),
• OPTIONAL: absent ⇒ the identity holds, the slot IS the on-disk index.

Lives in types/ (the bottom layer) so both rendering/ (depth-sort coordinator, picking) and data/ (commit pipeline, scene loader) share one definition without violating layer direction.