fix(discovery): backport served model aliases to 1.5 (#14857)

[jthomson04]

Summary

Backport #14857 to release/1.5.0. Workers that use the same non-empty model source path can register different, non-overlapping served names on one endpoint. Each served name selects its own worker group. Base/LoRA name collisions remain rejected.

Details

• Cherry-pick of a5c242e8269737313bdac98ef82822e6f04b99b9; applied without conflicts. Production changes are unchanged from the source PR.
• Adapt the test to release APIs: omit DistributedConfig::response_plane and use the loopback interface name for the TCP response stream.
• Check removal of one model registration and routing to the remaining alias before transport cleanup. Release 1.5 endpoint shutdown removes all same-name handlers in one process, so the two mock workers must defer that cleanup. This regression covers model removal; it does not verify independent shutdown of shared-process TCP endpoints.
• Preserve equal-primary-name compatibility, exact source-path comparison, and the existing model-card checksum and admission rules.
• The release branch has the required model-specific worker admission filter. Upgrade frontends and all participating workers to versions with that filter and this fix before enabling different primary served names on a shared endpoint.

Where should the reviewer start?

lib/runtime/src/discovery/mod.rs for registration compatibility, then the regression tests in lib/runtime/src/discovery/mock.rs and lib/llm/src/discovery/watcher.rs.

Related Issues

• Relates to fix(discovery): allow served aliases for the same model source #14857 and DYN-4449.

Validation

Run locally on the release backport with default test parallelism:

• cargo test -p dynamo-runtime --no-default-features --lib discovery::mock::tests — 15 passed.
• cargo test -p dynamo-llm --no-default-features --lib discovery::watcher::tests — 23 passed. Includes two classify workers using file discovery and TCP requests, separate alias routing, and removal of one model registration.
• cargo fmt --all -- --check and git diff --check HEAD^ HEAD — passed.

No GPU/vLLM end-to-end test was run.

[dynamo-review-agent]

This only restates the immediately following equal-display_name condition. “Existing” compatibility does not identify a lasting constraint beyond what the code already expresses.

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