fix: normalize gRPC agent card URLs

[muscariello]

Summary

This completes the remaining Rust-side gRPC interop fix by normalizing published gRPC agent-card interface URLs.

• canonicalize GRPC interface URLs by stripping plaintext http:// on construction and wire serialization/deserialization
• apply the same normalization in protobuf agent interface conversion so JSON and protobuf card paths stay aligned
• add regression tests for gRPC interface normalization and related error/status mappings used to keep overall line coverage above the current target

Context

The previously released Rust gRPC fix made the client tolerant of bare host:port endpoints. The remaining gap was on the publication side: Rust still emitted http://host:port in gRPC agent cards, which Go rejects for gRPC transport discovery. This change fixes that outbound card representation.

https:// URLs are intentionally preserved so TLS intent is not discarded.

Testing

• cargo fmt --all --check
• cargo test --workspace
• cargo clippy --workspace --all-targets -- -D warnings
• cargo llvm-cov --workspace --summary-only --ignore-filename-regex gen/ (95.08% line coverage)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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