The `stats:` line's decode-path tag is derived from the DecodedImage variant,
and both D3D11VA rungs deliver DecodedImage::D3d11 — they share the hand-off
ring on purpose. So a native-d3d11va session and an FFmpeg-d3d11va session
emitted a byte-identical tag, and nothing downstream could tell them apart.
The native Vulkan rung never had this: it carries its own variant, hence its
own `native-vulkan` tag.
That is not cosmetic, and it was found the only way it could be — by running
the rung on glass and having to grep the log to prove which one had answered.
A native pin that fails to initialise falls through to the FFmpeg rung by
design; the line it then emits is exactly the line the native rung would have
emitted. M5's owed soak and M9's vendor-matrix bake both rest on attributing
a session to a rung, and until now the machine-readable half of that evidence
could not do it. This project has already shipped one measurement that could
not tell "clean" from "unmeasured"; this is the same shape.
D3d11Frame now records which rung wrote the surface, keyed off the pin
constant itself rather than a second field the two rungs could set
inconsistently — the native rung passes DECODER_PIN into the hand-off and
nothing else does.
The stats line stays additive for every shipping session: the only value that
changes belongs to a rung that is pin-only and deliberately absent from the
automatic ladder, and the Windows shell passes the line through opaquely
rather than matching on the tag.
Verified on glass on .173, both directions: pinned native-d3d11va gives 85
windows tagged `native-d3d11va` and 0 plain, pinned d3d11va gives 64 plain and
0 native, zero errors either way. Gates: clippy -D warnings on Windows, the
Linux container's clippy/tests/workspace check, rustfmt.
enricobuehler
1573a9876b