test(backend): cover Preserve & Rerun across the run boundary

[vishnuv688]

What & why

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Polish (an improvement to an existing feature)
• Breaking change (existing behavior changes for users)
• Documentation
• Internal (build, CI, dependencies, tooling)

Packages touched

• shared (types and contracts)
• core (framework-agnostic capture/reporting)
• elements (published element/snapshot API — @wdio/elements)
• service (WebdriverIO adapter)
• nightwatch-devtools (Nightwatch adapter)
• selenium-devtools (Selenium adapter)
• backend (server)
• app (UI)
• script (page-injected runtime)
• selenium-devtools-py

Notes for reviewers

Screenshots / recordings

[greptile-apps]

Greptile Summary

This PR adds backend integration coverage for Preserve & Rerun across newly spawned run identities and documents the behavior for the Python Selenium adapter.

• Uses the real runner path so the next worker connection consumes rerun-child state.
• Verifies baseline retention, ordinary-rerun cleanup, cross-run comparison, terminal-triggered runs, and preservation of unaffected sibling tests.
• Documents Preserve & Rerun semantics and updates the adapter roadmap.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains; the newly added sibling-preservation scenario resolves the previously reported coverage gap by failing if the rerun worker is handled as an ordinary new run.

Important Files Changed

Filename	Overview
packages/backend/tests/preserve-across-rerun.test.ts	Adds deterministic end-to-end backend coverage using the real runner path, including a sibling-preservation assertion that distinguishes rerun-child continuity from an ordinary new-run reset.
packages/selenium-devtools-py/README.md	Documents Preserve & Rerun behavior and updates the implementation roadmap consistently with the covered backend behavior.
CLAUDE.md	Records the capability-gate and baseline-lifecycle rationale behind Preserve & Rerun.

Sequence Diagram

sequenceDiagram
  participant W1 as Original worker
  participant B as Backend
  participant R as Test runner
  participant W2 as Rerun worker
  W1->>B: Report failed attempt and sibling
  B->>B: Preserve selected baseline
  B->>R: Request rerun with preserveBaseline
  R->>R: Arm rerun-child state and spawn process
  W2->>B: Connect with new run ID
  B->>B: Consume rerun-child state without resetting active run
  W2->>B: Report rerun attempt
  B-->>W2: Baseline and latest remain comparable

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