fix: drop Intel Mac CI target, fix feature-gate dependency chain

ort-sys v2.0.0-rc.11 has no prebuilt ONNX Runtime binaries for
x86_64-apple-darwin, and vestige-mcp requires embeddings to compile.

- Remove x86_64-apple-darwin from CI release matrix (discontinued 2020)
- Fix vestige-mcp Cargo.toml: add default-features=false to vestige-core dep
- Extract sanitize_fts5_query to always-available fts.rs module
- Gate embeddings-only imports in storage/sqlite.rs behind #[cfg]

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -59,9 +59,9 @@ jobs:
           - os: macos-latest
             target: aarch64-apple-darwin
             cargo_flags: ""
-          - os: macos-14
-            target: x86_64-apple-darwin
-            cargo_flags: "--no-default-features"
+          # x86_64-apple-darwin dropped: ort-sys has no prebuilt ONNX Runtime
+          # binaries for Intel Mac, and the codebase requires embeddings.
+          # Apple discontinued Intel Macs in 2020. Build from source if needed.
           - os: ubuntu-latest
             target: x86_64-unknown-linux-gnu
             cargo_flags: ""