Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

Per-vertex GS fog end-to-end (gs_stub emit incl. persp_emit5, gs_prim_list_feeder
XYZ2->XYZF2 on PRIM.FGE, gs_make_sh3_scheduler_fixture.py F/FGE packing), new fog
TBs, fidelity attribution tooling. Functional baseline before removing the dead
bilinear lerp8 clamps (Codex: 161-node comb loop -> -0.042ns setup fail).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/ch374_audit_log.md

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+# Ch374 Audit Log - Earlier-Capture Eleven-Draw Rebind Expansion
+
+## Fixture
+
+- `zsrte11` keeps Ch373's eight chronological draws as three runtime-CLUT epochs, then adds draws
+  `11698`, `11911`, and `11938` as a fourth 142-triangle epoch.
+- The scene runs at native 640x480 and allocates two runtime palette banks: CBP `504` for epochs 0-2
+  and CBP `508` for epoch 3. The residency pattern is `fill, reuse, reuse, fresh fill`.
+- Feeder lists contain 1,843, 1,843, 817, and 1,285 words, each below the 4,096-word bridge capacity.
+
+## Integration Gate
+
+- Depth-4096 integration passes with 524,145 accepted fragments, 431,666 persistent-Z updates, four fresh drains,
+  and zero drops.
+- Epoch request-FIFO high-water is 2,090, 940, 1,757, and 100. Exact scoreboards report Z `0/307200` and
+  color `0/129883` mismatches.
+
+## Board Host Gate
+
+- The DE25 completed the two texture fills, two resident CRC checks, four runtime palette copies, all 640 expected
+  records, and zero fragment drops.
+- The board framebuffer has 129,883 nonzero words in bounds `(65,41)..(462,470)`.
+
+## Silicon Closure
+
+- Board and traced-integration framebuffers are byte-identical at SHA-256
+  `b44f5e98d79ffa2f451238182f798432edb5c413ea80fea2da6c231a0b4be151`.
+- The complete trace independently replays to the board framebuffer exactly: 524,145 fragments,
+  431,666 Z-pass updates, 129,883 covered pixels, zero uncovered writes, and `307200/307200` exact colors.
+
+## Result
+
+Ch374 closes the first two-palette, eleven-draw earlier-capture expansion on silicon with no RTL, constraint,
+or fit change.