feat(stargate): add configurable Pulsar input TPS weights

[barrygreengus]

TL;DR

Add an optional generation maximum input TPS measurement from Pylon through Stargate, and let Pulsar rendezvous routing select either the existing mean or that maximum as its capacity weight. Mean input TPS remains the default.

Additional Details

Pylon publishes the maximum already maintained by its generation-owned input TPS distribution. The value persists for that model generation and resets when the generation is replaced. There is no time window, bucket state, expiration path, or related runtime configuration.

Stargate sums the optional maximum only when every backend in the cluster supplies a valid positive finite value. Pulsar and Pulsar wait-and-widen accept last-mean-input-tps or max-input-tps for rendezvous weighting. Max mode does not silently fall back to mean when peak data is incomplete. Admission and work estimation continue using mean.

The ranking cache keys include the selected weight, so changing the unused statistic does not invalidate cached rankings. No dependencies or hash-version behavior changed.

For the Reviewer

Please focus on generation ownership and reset behavior, complete-only aggregation across mixed versions, and consistency between ranking cache invalidation and weight selection.

For QA

QA is not required beyond automated coverage. Verified with:

• cargo fmt --all --check
• cargo test -p pylon-lib --quiet
• cargo test -p pylon --quiet
• cargo test -p stargate --quiet
• Bazel tests for pylon-lib, pylon, and stargate

Issues

Closes #1001

Checklist

• I am familiar with the Contributing Guidelines.
• I have signed off my commits for Developer Certificate of Origin compliance.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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[github-actions]

🛡️ CodeQL Analysis

🚨 Found 2 issue(s)

Severity Breakdown:

• 🔴 Errors: 0
• 🟡 Warnings: 0
• 🔵 Notes: 0

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_{🕐 Last updated: 2026-08-19 15:47:50 UTC | Commit: f00fe01}