Gather every model under one tree at the repository root

The weights were in two places: face detection and recognition in
`models/face/`, segmentation in `core/dr-segment/models/`. Nothing was
wrong with either path, but between them there was nowhere to look to
answer "how much model does this application carry", and that number is
about to start growing.

So the crate-local copy moves up beside the other. `models/` now holds
`face/` and `segment/`, and a `du -sh` of one directory is the whole
answer.

No content changes: the .onnx and its vocabulary are byte-identical, and
`LICENCE.md` moves up a level to cover the tree rather than one crate.
The LFS pattern in `.gitattributes` is `*.onnx` and already matched both
locations, so only its comment needed the new path.

`include_bytes!` is relative to the source file and `build.rs` runs with
the crate root as its working directory, which is why the two paths climb
a different number of levels.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

core/dr-segment/src/lib.rs

@@ -26,7 +26,7 @@
 //!
 //! That combination is also what repairs the vocabulary problem. The shipped
 //! model is COCO-trained, so it recognises subjects and has no class for sky,
-//! foliage or wall (`models/LICENCE.md`). Selecting those falls to arm A,
+//! foliage or wall (`models/LICENCE.md` at the repository root). Selecting those falls to arm A,
 //! which never needed a vocabulary to begin with.
 
 pub mod distance;