ci(e2e): queue E2E runs for the owned pool within CI_PR_POOL_QUEUE_ROUNDS

[teamleaderleo]

Why

Follow-up to #14630 (same cause, E2E side). e2e_runner_pool.py read no CI_PR_POOL_QUEUE_ROUNDS, so an E2E run took an owned pool only when its peak was free, with every in-flight run's whole future peak (committed) counted as taken. Pull request CI dropped that rule in #14401. On the 2026-09-25 12:34:57 snapshot it read 43 of 32 std machines taken while 8 ran, so every owned pool looked full.

What

• test-e2e.yml passes --queue-rounds "$POOL_QUEUE_ROUNDS" (vars.CI_PR_POOL_QUEUE_ROUNDS; "" is the default 1 round, 0 the kill switch, omitted is 0). dispatch-focused-test.py reads the same variable (unset is the default), and test-macos-suite.yml and main-regression-bisect.yml pass it through as CMUX_CI_PR_POOL_QUEUE_ROUNDS.
• The rounds decide only whether an owned pool takes the run. When none does, e2e_runner_pool.decide() picks Blacksmith by E2E's unchanged headroom rule (first free machine, then the shorter queue), so the Blacksmith behavior and its tests stay the same.
• owned_pool_rescue.py gives test-e2e.yml runs the same queue_seconds() allowance as ci.yml and test-ios.yml runs.

Tests

• Replaying the real 12:34:57 snapshot: rounds 0 or omitted stays on Blacksmith ("every pool is full"). With 2 rounds and 13 replayed PR runs, the run joins an owned root queue within 20 min. With 22 or 40 replayed runs the Blacksmith pick is the same as rounds 0.
• python3 tests/test_ci_pr_runner_pool.py 161 OK, tests/test_ci_owned_pool_rescue.py 92 OK, tests/test_run_e2e.py 101 OK, plus workflow_run_sources, fork routing and the self-hosted guard.

Design note from review: an E2E build or test job holds a root runner up to about 45 min, longer than the compile-length round the queue estimate assumes. So on the 2-runner glaeda-root-light pool, a queued E2E run can delay PR admission for longer than the rounds suggest. Setting CI_PR_POOL_QUEUE_ROUNDS to 0 turns this off.

🤖 Generated with Claude Code

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Summary by cubic

Makes E2E runs queue for owned macOS pools within CI_PR_POOL_QUEUE_ROUNDS, matching pull request CI. Previously E2E used the kill-switch rule, which counted every in-flight run's whole future peak as taken now, so owned pools frequently looked full and runs fell back to Blacksmith.

• The rounds decide only whether an owned pool takes the run; when none does, the Blacksmith pick stays on the unchanged headroom rule.
• The workflows and dispatch launcher now pass CI_PR_POOL_QUEUE_ROUNDS through: "" is the default of 1 round, 0 turns the feature off, and an omitted flag keeps the old behavior.
• owned_pool_rescue.py gives E2E runs the same queue allowance as ci.yml and test-ios.yml runs.
• An E2E job holds a root runner up to about 45 minutes, longer than the round the queue estimate assumes, so set the variable to 0 to turn this off.

^{Written for commit 2670287. Summary will update on new commits.}

[github-actions]

Merge receipt for 2670287f91, merged 2026-09-25 13:22:08 UTC

• Not verified at merge: ci-status (not reported), Web complexity (not reported), web-validation (not reported)
• Full suite: runs on main after merge.

Labeled merged-unverified: if main breaks near this merge, look here first.

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Reviewing files that changed from the base of the PR and between 27b8cbc and 2670287.

📒 Files selected for processing (9)

• .github/workflows/main-regression-bisect.yml
• .github/workflows/test-e2e.yml
• .github/workflows/test-macos-suite.yml
• scripts/ci/dispatch-focused-test.py
• scripts/ci/e2e_runner_pool.py
• scripts/ci/owned_pool_rescue.py
• tests/test_ci_owned_pool_rescue.py
• tests/test_ci_pr_runner_pool.py
• tests/test_run_e2e.py

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