Three gaps the previous round left, all in the same key-resolution rule, so the
rule now lives in one place as split_quant_suffix.
A quant label may carry a bits-per-weight modifier, because two files at the
same base quant are kept distinct by it: utils/models/model_config.py preserves
IQ4_XS-3.53bpw while hub/utils/gguf.py strips it, and both forms reach the
override keys. The known-quant pattern accepted neither, so _bare_model_id
missed the bare entry and the first qualified save dropped its launch flags.
On POSIX the browser lowercases the quant but keeps the path casing, so a
migrated "/models/Foo:q4_k_m" was unreachable from the scanner's
"/models/Foo:Q4_K_M". Only the quant suffix folds now, and only when it really
is a quant, so "/models/foo:Bar.gguf" stays a distinct filename and the path
itself stays case-sensitive.
A standalone .gguf picked directly has no quant to choose between and is stored
with a null variant. The backfill filter read that as safetensors and skipped
it, and the done flag is set on the same pass, so those settings stayed
browser-only for good while auto-switch kept loading the model with defaults.
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