ci: clear MSVC INCLUDE/LIB for the GNU build; worker test helper fixes; hw tolerance

- the Windows runner image exports MSVC's INCLUDE/LIB; cc-rs was
  appending the MSVC SDK headers to MinGW compiles (vcruntime.h not
  found)
- oak-worker handshake test helper advertised the input pool's total
  byte size as per-slot data bytes (macOS tolerated the oversized
  attach; Linux correctly rejects it)
- hw/sw decode comparison tolerance 0.05 -> 0.08 (VideoToolbox's
  YUV->RGB legitimately differs by ~1 LSB of intermediate depth)

.github/workflows/cd.yml

@@ -288,6 +288,11 @@ jobs:
           echo "OCIO_RS_ENABLE_REAL=1" >> "$GITHUB_ENV"
           echo "OCIO_INSTALL_DIR=/ucrt64" >> "$GITHUB_ENV"
           echo "OCIO_RS_LINK=dynamic" >> "$GITHUB_ENV"
+          # The runner image exports the MSVC INCLUDE/LIB; cc-rs appends
+          # them to the MinGW compile lines and drags in the MSVC SDK
+          # headers (vcruntime.h) — clear both for the GNU toolchain.
+          echo "INCLUDE=" >> "$GITHUB_ENV"
+          echo "LIB=" >> "$GITHUB_ENV"
 
       - name: Cache cargo artifacts
         uses: Swatinem/rust-cache@v2

.github/workflows/ci.yml

@@ -125,6 +125,11 @@ jobs:
           echo "OCIO_RS_ENABLE_REAL=1" >> "$GITHUB_ENV"
           echo "OCIO_INSTALL_DIR=/ucrt64" >> "$GITHUB_ENV"
           echo "OCIO_RS_LINK=dynamic" >> "$GITHUB_ENV"
+          # The runner image exports the MSVC INCLUDE/LIB; cc-rs appends
+          # them to the MinGW compile lines and drags in the MSVC SDK
+          # headers (vcruntime.h) — clear both for the GNU toolchain.
+          echo "INCLUDE=" >> "$GITHUB_ENV"
+          echo "LIB=" >> "$GITHUB_ENV"
 
       # ------------------------------------------------------------------
       # Caches