Separate console CI routing and verification

[AbigailDeng]

Problem and solution

Repository-wide CI policy was mixed into Workflow Activity vNext integration PR #3187. Extract it into an independently reviewable CI-only PR targeting dev.

• Run frontend Jest tests in four partitions and keep the existing required console-web gate dependent on all partitions succeeding.
• Route backend coverage by the actual changed-file scope, not a feature branch name. Strictly frontend-only PRs skip backend coverage; mixed changes, CI/build changes and scheduled/manual/mainline verification retain it.
• Run the optional workflow canvas benchmark only when its checked-in Playwright config exists. This makes the CI change standalone on current dev, which does not yet include the vNext benchmark package scripts/assets.
• Add routing and benchmark-capability regression checks.

Impacted paths

Only .github/workflows/ci.yml and tools/ci/tests/test_ci_change_scope.py change. No frontend production code, backend code, dependencies or API contracts are included.

Local verification

• python3 tools/ci/tests/test_ci_change_scope.py — 4 tests passed.
• PATH=/opt/homebrew/opt/python@3.12/libexec/bin:$PATH bash tools/ci/test_stability_guards.sh — passed, including guard meta-tests. The initial system Python 3.9 invocation was incompatible with an existing Python 3.10+ annotation; rerunning with Python 3.12 resolved the environment issue without modifying unrelated code.
• git diff --check — passed.
• Full frontend suite/typecheck/production build: delegated to GitHub CI by personal local-validation policy; not run locally.

Independent integration

This CI PR is optional and independent of frontend PR #3187. Both target dev directly. The frontend PR restores repository CI files to dev's baseline and has no repository CI changes in its dev comparison, so there is no required merge order and rejecting this CI proposal does not block frontend integration. No backend merge into dev is required for the frontend work; feature/integrate remains its backend contract baseline.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.43%. Comparing base (1df08db) to head (4a8e805).

@@            Coverage Diff             @@
##              dev    #3697      +/-   ##
==========================================
- Coverage   83.44%   83.43%   -0.01%     
==========================================
  Files        1685     1685              
  Lines      193217   193217              
  Branches    23239    23239              
==========================================
- Hits       161221   161212       -9     
- Misses      21186    21191       +5     
- Partials    10810    10814       +4     

Flag	Coverage Δ
ci	83.43% <ø> (-0.01%)	⬇️

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see 8 files with indirect coverage changes

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