docs: clarify Hugging Face loading for Kronos models

[chethanuk]

What changed

• pin the README Hugging Face loading example to known tokenizer/model revisions
• document the supported loading path via the local model classes and note force_download=True for stale cache mismatches

Why it matters

• gives users a repo-supported loading snippet for the released Hub artifacts
• addresses confusion around config.json and initialization errors when local caches are out of date

Validation

• git diff --check
• confirmed config.json exists in NeoQuasar/Kronos-Tokenizer-base and NeoQuasar/Kronos-small
• confirmed the pinned revisions exist on the Hugging Face Hub

Fixes #240