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>

tools/gs_merge_scheduler_bootlets.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+"""Build one scheduler bootlet that preloads the distinct CLUTs required by several fixture tags.
+
+Usage: gs_merge_scheduler_bootlets.py <output-tag> <input-tag> [<input-tag> ...]
+"""
+import os
+import re
+import sys
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+ROOT = os.path.normpath(os.path.join(HERE, ".."))
+DATA = os.path.join(ROOT, "sim", "data", "top_psmct32_raster_demo")
+sys.path.insert(0, DATA)
+import bake
+
+RAM_QWORDS = 512
+HEADER_QWORDS = 16
+FBW = 10
+FBPXW = 640
+FBH = 480
+
+
+def read_payload(tag):
+    path = os.path.join(DATA, f"payload_sh3_{tag}.mem")
+    with open(path) as f:
+        lines = f.readlines()
+    header = next((line for line in lines if line.startswith("//")), "")
+    match = re.search(r"QWC=(\d+)", header)
+    if not match:
+        raise ValueError(f"{path}: missing QWC metadata")
+    cbp_match = re.search(r"CBPs \[([^]]*)\]", header)
+    if not cbp_match:
+        raise ValueError(f"{path}: missing CBP metadata")
+    cbps = [int(x.strip()) for x in cbp_match.group(1).split(",") if x.strip()]
+    words = [int(line.strip(), 16) for line in lines if line.strip() and not line.startswith("//")]
+    if len(words) != RAM_QWORDS:
+        raise ValueError(f"{path}: expected {RAM_QWORDS} qwords, got {len(words)}")
+    qwc = int(match.group(1))
+    if qwc > RAM_QWORDS - HEADER_QWORDS:
+        raise ValueError(f"{path}: QWC {qwc} exceeds payload capacity")
+    return qwc, cbps, words[HEADER_QWORDS:HEADER_QWORDS + qwc]
+
+
+def main(argv):
+    if len(argv) < 4:
+        print(__doc__.strip())
+        return 2
+    output_tag, input_tags = argv[1], argv[2:]
+    active = []
+    seen_cbps = set()
+    for tag in input_tags:
+        qwc, cbps, words = read_payload(tag)
+        for cbp in set(cbps):
+            if cbp in seen_cbps:
+                raise ValueError(f"duplicate relocated CBP {cbp}: fixture {tag} aliases an earlier input")
+            seen_cbps.add(cbp)
+        if len(words) != qwc:
+            raise ValueError(f"payload word count mismatch for {tag}")
+        active.extend(words)
+    if len(active) > RAM_QWORDS - HEADER_QWORDS:
+        raise ValueError(f"combined QWC {len(active)} exceeds {RAM_QWORDS - HEADER_QWORDS}")
+
+    payload_name = f"payload_sh3_{output_tag}.mem"
+    bios_name = f"bios_sh3_{output_tag}.mem"
+    with open(os.path.join(DATA, payload_name), "w") as f:
+        f.write(f"// combined scheduler CLUT preload tags={input_tags} CBPs={sorted(seen_cbps)} QWC={len(active)}. gitignored.\n")
+        for _ in range(HEADER_QWORDS):
+            f.write("00000000000000000000000000000000\n")
+        for word in active:
+            f.write(f"{word:032x}\n")
+        for _ in range(RAM_QWORDS - HEADER_QWORDS - len(active)):
+            f.write("00000000000000000000000000000000\n")
+    display1_hi = ((FBH - 1) << 12) | (FBPXW - 1)
+    bake.write_bios_mem(
+        bios_name,
+        bake.build_textured_demo_bootlet_disp(len(active), display1_hi, FBW),
+        f"combined scheduler CLUT preload tags={input_tags} QWC={len(active)} DISPLAY1={FBPXW}x{FBH}. gitignored.",
+    )
+    print(f"[bootlet] emitted {bios_name} + {payload_name}: QWC={len(active)} CBPs={sorted(seen_cbps)}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main(sys.argv))