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/ch367_audit_log.md

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+# Ch367 Audit Log - Runtime CLUT At 24 Draws
+
+## Scope
+
+Join the established native-640x480 24-draw shared-texture cluster to the runtime CLUT transport. The fixture has
+eight ordered 204-record epochs, one texture fill, seven CRC-verified residency reuses, and a host runtime palette
+copy before every epoch.
+
+## FIFO Sizing
+
+- At request depth 1024, the runtime fixture removes the boot-time CLUT-loader throttle and epoch 2 dropped 19
+  fragments after the high-water counter saturated at 1024.
+- At depth 2048, epoch 2 accepted all 58,861 fragments at high-water 1041. Integration simulation also passed
+  epochs 0 through 6 with zero drops; epoch 5 was the largest observed simulation burst at 1855.
+- The DE25 top therefore changes only `u_zc_emit` request depth from 1024 to 2048. No clock, SDC, or protocol
+  change is involved; `zc_g_drops` remains the fail-closed hardware guard.
+
+## GUI Fit And Board Gate (2026-07-12)
+
+- Quartus 26.1 STA finished at 08:40:47 and met every requirement: setup +0.090 ns, hold 0.000 ns, recovery
+  +1.043 ns, removal +0.201 ns, and minimum pulse width +0.200 ns.
+- The 08:41 core RBF SHA-256 is `8e3fa2b8b14de9b4660a542ec7ffed5c59353ec8583458f31339a4b4183f42d2`; fit reports
+  the request FIFO as a 2048 x 74 dual-clock M20K implementation.
+- The RBF was SHA-verified on the DE25 and loaded through `core_loader.sh`; `fpga0` reported `operating` and the
+  overlay reported `applied`.
+- Board scheduler gate: all eight 204-record epochs drained freshly; one texture CRC-verified fill and seven
+  resident CRC checks passed; every runtime palette sum was `0x47097d4c`; every epoch reported zero drops.
+- Board dump: 73,330 nonzero pixels, bounds `(84,85)..(568,399)`, sum `0xc521381a`, xor `0x8021455e`.
+
+## Exact Closure
+
+- The trace-enabled integration run passed all eight epochs: 346,425 accepted fragments, 167,247 persistent-Z
+  updates, eight scene markers/drains, zero drops, and exact local scoreboards (Z `0/307200`, color `0/73330`).
+- The highest simulated request-FIFO occupancy was 1855 in epoch 5; the final epoch reached 1156. Both remain below
+  the production 2048 entries and agree with the board's zero-drop counters.
+- Board and integration-simulation framebuffers are byte-identical with SHA-256
+  `6614d7211b9a668cfeda12e4fa2d6f469d3ee4d3a10bdf56c0119b35f93c7803`.
+- Replay-color is exact at `307200/307200` pixels: 346,425 fragments, 167,247 Z-pass updates, 73,330 covered
+  pixels, and zero uncovered writes.
+
+## Result
+
+Ch367 is closed on silicon: 24 authentic SH3 draws, runtime CLUT staging on every epoch, one texture fill plus
+seven verified resident reuses, native 640x480 scanout, and persistent depth all agree with integration simulation
+and the independent replay oracle.