docs: align README with current surfaces

[localai-org-maint-bot]

What changed

• update the README from 37 to 40 registered architectures
• update tool parsing from 36 families and 40 names to 38 families and 42 names
• update the documented C ABI from v19 to v21
• add the gated MiniMax-Music3 server path to News
• remove the superseded Vulkan benchmark from News while retaining it in the hardware section with its caveat

Why

The README had fallen behind the source registry, parser factories, public ABI, and current feature ledger. MiniMax-Music3 is now a user-visible generation lane with every model stage and a real HTTP request gated. Its device path remains partial, and the README makes no speed claim.

Verification

python3 scripts/check-readme-structure.py
python3 scripts/check-supported-models.py
python3 scripts/check-doc-checkpoint.py
python3 scripts/check-agent-record.py
python3 scripts/check-model-checklist.py
python3 scripts/check-public-doc-tables.py
python3 scripts/check-env-doc.py
python3 tests/scripts/test_check_readme_structure.py
python3 tests/scripts/test_check_supported_models.py
python3 tests/scripts/test_doc_checkpoint.py
python3 tests/scripts/test_check_public_doc_tables.py
python3 tests/scripts/test_check_env_doc.py
git diff --check upstream/main...HEAD

All checks pass. This documentation-only change requires no GPU verification.