docs(perf): close Slice B with full-bake evidence

docs/research/2026-07-24-slice-b-full-bake-report.md

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+# Slice B full-bake report
+
+**Date:** 2026-07-24  
+**Measured binary:** `90bf6bbf455654dd1cfe1749b19bfd36b769939c`  
+**Result:** pass, zero extraction failures
+
+Slice B replaces the failed 865 GB per-cell bake with a deterministic,
+content-identity package. The client does not consume this package yet; this is
+the offline prepared-content foundation for Slice C.
+
+## Full installed-DAT result
+
+| Measure | Result |
+|---|---:|
+| GfxObj keys | 15,318 |
+| Setup keys | 5,935 |
+| EnvCell keys | 729,888 |
+| Unique EnvCell geometries | 17,117 |
+| EnvCell aliases | 712,771 |
+| EnvCell deduplication | 42.6× |
+| Physical blobs | 38,370 |
+| Total TOC keys | 751,141 |
+| Failures | 0 |
+| Extract + write | 81.2 seconds |
+| Validate + atomic publish total | 81.4 seconds |
+| Artifact size | 29,561,864,760 bytes (28,192.4 MiB) |
+| Peak working set | 5,073.7 MiB |
+| Peak private bytes | 4,507.3 MiB |
+
+The memory figures belong to the short-lived offline bake process while it
+constructs and serializes 28.2 GiB of immutable payloads. They are not expected
+client residency: the later runtime source memory-maps the package and
+deserializes only demanded assets. Sixteen-result extraction batches and
+immediate rejection of already-written side-staged meshes keep live bake graphs
+bounded; 13,284 redundant particle-preload results were discarded without
+retention.
+
+The header carries format version 1, bake-tool version 2, and source DAT
+iterations portal 2072, cell 982, high-res 497, language 994. Validation opened
+the completed temporary package, checked those values, strict TOC ordering,
+all 751,141 physical ranges, and then published with a same-volume atomic
+overwrite move. No temporary artifact remained.
+
+## Identity correction discovered by the gate
+
+The first guarded full catalog stopped on a real collision in WorldBuilder’s
+31× polynomial:
+
+- Cell `0x00030175`: environment `0x277`, structure 0, surfaces
+  `0x013B, 0x0034`.
+- Cell `0x01BC0105`: environment `0x276`, structure 0, surfaces
+  `0x04FC, 0x0034`.
+- Both legacy identities: `0x00000002020E8C13`.
+
+Those cells have different vertices and polygons. Silently aliasing them would
+render the wrong room. Runtime and bake now share a namespaced FNV-1a identity
+over the complete typed tuple, while the catalog still compares full tuples and
+fails loudly on any future collision. The legacy calculation remains as a
+conformance test proving this exact installed-DAT case.
+
+## Alias and determinism gates
+
+A sampled physical receipt at offset `16170873792` is shared by 25 EnvCell keys
+across multiple landblocks. Eight of those keys were baked independently with
+one and eight workers. Each output contained eight keys backed by one physical
+blob, and both files were byte-identical:
+
+`C8187761ED30CE9412C9081F52067159AECA5B02EB316E73DA29DC88D4339642`
+
+The generated full pak remains an untracked machine artifact and is deleted
+after final verification. The machine-readable, path-free evidence is
+[`2026-07-24-slice-b-full-bake-report.json`](2026-07-24-slice-b-full-bake-report.json).
+
+Release build passed with 17 pre-existing test-source warnings. The complete
+Release suite passed 8,059 tests with five skips and zero failures. The generated
+full and filtered pak artifacts were then deleted as required.