fix(tests): add CI failure tolerance and fix 4 embedding tests (Section 5/5)

[yehudit1987]

Fix 4 skipped embedding tests (GetEmbeddingSmart, GetEmbeddingWithDim,
EmbeddingConsistency, EmbeddingPriorityRouting) while maintaining CI
stability for other contributors.

Changes:

• Add HF_TOKEN support for gated models (embeddinggemma-300m) in CI
• Fix Rust OnceLock re-initialization and add model availability fallback
• Add graceful dimension degradation for Matryoshka embeddings
• Fix .downloaded marker files to ensure complete model downloads
• Restore test failure tolerance in CI to prevent blocking other PRs

⚠️ IMPORTANT: GATED MODEL REQUIREMENTS ⚠️

The embeddinggemma-300m model is GATED by Google and requires:

1. Accept terms at: https://huggingface.co/google/embeddinggemma-300m
2. Create HF token at: https://huggingface.co/settings/tokens
3. Add HF_TOKEN to GitHub repository secrets

===========================================

The tests now pass when models are available, but failures are tolerated
in CI to avoid breaking other contributors' builds.

Fix Partially issue #573

[netlify]

✅ Deploy Preview for vllm-semantic-router ready!

Name	Link
🔨 Latest commit	5cc12a3
🔍 Latest deploy log	https://app.netlify.com/projects/vllm-semantic-router/deploys/6911fd2589ef860008044ab2
😎 Deploy Preview	https://deploy-preview-623--vllm-semantic-router.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[github-actions]

👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 Root Directory

Owners: @rootfs, @Xunzhuo
Files changed:

• .github/workflows/test-and-build.yml

📁 candle-binding

Owners: @rootfs
Files changed:

• candle-binding/semantic-router_test.go
• candle-binding/src/classifiers/unified.rs
• candle-binding/src/ffi/embedding.rs

📁 tools

Owners: @yuluo-yx, @rootfs, @Xunzhuo
Files changed:

• tools/make/models.mk
• tools/make/rust.mk

---

🎉 Thanks for your contributions!

This comment was automatically generated based on the OWNER files in the repository.