config(multi-config): fix GGUF dispatch + per-config-id measured persistence

Follow-up to the same-path multi-config runtime fix. Two more path-keyed spots
broke a same-file sibling addressed by its alias (e.g. lisa-32k):

1) GGUF dispatch: _resolve_local_gguf matched entries by path/basename only, so
   a sibling addressed by alias wasn't recognized as GGUF and fell to the HF
   loader ("lisa-32k is not a valid model identifier"). Now also match the
   entry's alias.

2) Measured footprint cross-contamination: persist_model_field matched entries
   by path, so one config's measured_vram_gb/n_gpu_layers overwrote the sibling's
   — the small-ctx variant inherited the large-ctx footprint (34 GB) and still
   offloaded to CPU. persist_model_field now targets by config_id when given;
   record_vram_delta passes cfg['config_id']; _model_cfg carries config_id/
   config_name so the config knows its own entry identity.

Net: lisa (178K) and lisa-32k (32K) are now fully independent — distinct config,
GGUF load from the shared file, and separate measured footprints.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mw2KQiswmD69T45fTfjKwW