#24987 ci(nightly): overlap compatibility notarization and route pooled runners

Problem

nightly-next paid the compatibility identity after the main notarization and publication, while the release jobs also waited behind the hosted macOS pool.

Change

• Rebased and adopted the routing work from origin/nightly-any-machine@6da03b0c0d5 on the current feat-cmux-next line.
• Route Linux first, then the configured owned Mac pool, with the Blacksmith pool as fallback; no cancellation or eviction policy changes.
• Let the compatibility identity consume the prepared arm64 app and submit its temporary NEXT DMG while the main identity is in Apple's queue. Pending continuations keep the published artifact path.

Before/after

The same nightly.yml workflow's last five completed successful nightly-next runs before this branch: #40124133067 181m03s, #40121278753 199m10s, #40118942042 106m27s, #40117679682 204m08s, #40114588859 219m41s; median 199m10s. The after receipt will be recorded from one real post-merge nightly-next run.

Validation

• Parsed .github/workflows/nightly.yml with PyYAML.
• Parsed changed Python files and ran bash -n on the notarization scripts.
• CI fast checks are required on the exact PR head.

Changelog

none

Agent session: Air-Blue

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