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>

.gitignore

@@ -25,6 +25,16 @@ manifest.hex
 *sh3*.hex
 *sh3*.dat
 sh3_*.mem
+# Ch356/Ch357 epoch descriptor tables — dump-derived (dump indices + texture CRCs). Exact
+# paths only (a broad *sh3*.txt would wrongly ignore legitimate docs like *_sh3_notes.txt).
+/sim/data/top_psmct32_raster_demo/sh3_sched_epochs.txt
+/sim/data/top_psmct32_raster_demo/sh3_s640_epochs.txt
+/sim/data/top_psmct32_raster_demo/sh3_zsched_epochs.txt
+/sim/data/top_psmct32_raster_demo/sh3_ztrio_epochs.txt
+/sim/data/top_psmct32_raster_demo/sh3_zs640_epochs.txt
+/sim/data/top_psmct32_raster_demo/sh3_zs640c6_epochs.txt
+# dump-derived reference/board-FB images (render copyrighted game frames)
+/sim/data/top_psmct32_raster_demo/sh3_*.png
 
 # ---- python cache ----
 __pycache__/
@@ -40,6 +50,9 @@ __pycache__/
 /synth/**/dni/
 /synth/**/qdb/
 /synth/**/.qsys_edit/
+/synth/**/tmp-clearbox/
+/synth/**/sta_*.txt
+*.tdf
 /synth/de25_nano/top_psmct32_raster_demo/baseline_*/
 /synth/de25_nano/experiments/
 *.sof