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/ch375_audit_log.md

@@ -0,0 +1,13 @@
+# Ch375 Audit Log - Fourteen-Draw Post-Rebind Residency
+
+- `zsrte14` extends Ch374 with three later, on-screen draws using CBP `508`, producing a five-epoch
+  `fill, reuse, reuse, rebind, reuse` runtime-CLUT sequence at native 640x480.
+- Integration passes with 529,836 accepted fragments, 434,596 Z-pass updates, five fresh drains, zero drops,
+  exact Z `0/307200`, and exact color `0/132063`. Request-FIFO high-water is 2,090, 940, 1,757, 100, and 81.
+- On the DE25, both palette banks, both texture fills, all 816 expected records, and all drop gates pass.
+- Board and traced integration framebuffers are byte-identical at SHA-256
+  `3a4b8f12a08dd0a5e9872675a1dd7cf2d767b76c71def1c1f4398f8c89da104d`.
+- Replay-color is exact at `307200/307200`: 529,836 fragments, 434,596 Z-pass updates, 132,063 covered pixels,
+  and zero uncovered writes.
+
+Ch375 closes the fourteen-draw post-rebind residency expansion on silicon without RTL, constraint, or fit changes.