coli: measured Windows launcher defaults — OMP tuning parity + DIRECT/PIPE/PILOT_REAL

On Windows the engine self-exec OMP tuning never runs (Linux/FreeBSD-only)
and posix_fadvise readahead is a compat.h no-op, so a stock Windows run
leaves large measured wins on the table. The launcher now setdefaults, on
win32 only, each independently overridable by setting the variable:

- OMP_WAIT_POLICY=active, GOMP_SPINCOUNT=200000, OMP_DYNAMIC=FALSE,
  OMP_NUM_THREADS=<physical cores> (parity with the glm.c self-exec block;
  COLI_NO_OMP_TUNE disables exactly this block, presence-based like the
  engine). OMP_PROC_BIND/OMP_PLACES deliberately omitted and also removed
  from environment_for_plan on win32: MinGW libgomp has no affinity support
  ("Affinity not supported on this configuration").
- DIRECT=1: unbuffered expert reads. Measured on a 9950X3D + Samsung 9100
  PRO Gen5 + Win11: iobench 10.68 GB/s O_DIRECT vs 9.03 buffered (warm);
  end-to-end REPLAY 0.48 -> 1.02 tok/s. Matches #162 (1.47x same class).
- PIPE=1: load/matmul overlap, byte-identical output; +8% on top of DIRECT
  (PIPE_WORKERS untouched at 8 - 4/8/16 swept flat on Gen5).
- PILOT_REAL=1: real cross-layer prefetch, the only working prefetch on
  Windows; +11% and expert hit rate +19 points.

Full ladder methodology and numbers: 96-token greedy REPLAY, one lever per
step, medians of 3-4 runs (see the fork tuning doc referenced in the PR).
tests/test_env_defaults.py covers the defaults, explicit-override-wins,
the kill-switch scope, and the non-win32 no-op.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

c/resource_plan.py

@@ -313,8 +313,11 @@ def environment_for_plan(plan, env=None, cuda_enabled=True):
     result = dict(env or {})
     result.setdefault("COLI_POLICY", plan["policy"]["name"])
     result.setdefault("OMP_NUM_THREADS", str(plan["cpu"]["physical_cores"]))
-    result.setdefault("OMP_PROC_BIND", "spread")
-    result.setdefault("OMP_PLACES", "cores")
+    if sys.platform != "win32":
+        # la libgomp di MinGW non supporta l'affinity su Windows
+        # ("Affinity not supported on this configuration"): non impostarle li'.
+        result.setdefault("OMP_PROC_BIND", "spread")
+        result.setdefault("OMP_PLACES", "cores")
     if plan["policy"]["name"] == "balanced":
         result.setdefault("REPIN", "64")
     ram = plan["tiers"]["ram"]