refactor(pipeline): add PipelineError::reconstruct to de-duplicate outcome rematch

[nh13]

Summary

Pipeline::run (core/builder.rs) and the fused single-thread driver (core/runtime/fused.rs) each open-coded the same per-variant match to turn the borrowed signal.outcome(): Option<&PipelineError> into the owned error they return — necessary because PipelineError is not Clone (its Io variant holds a non-Clone io::Error). Extract that into PipelineError::reconstruct(&self) -> PipelineError; both call sites collapse to Some(err) => Err(err.reconstruct()).

Behavior preservation

Identical — the Io source is still rebuilt from kind() + display string, all other variants copied. A future error variant now needs handling in one place instead of two. Fused-pipeline and pipeline error-path tests pass unchanged.

Context

Third of the post-#330 subsystem-simplification cleanups (discovery bundle "pipeline misc"). Dual-reviewed before push (CLI: no findings; skill: 0 actionable).

[codecov]

Codecov Report

❌ Patch coverage is 96.00000% with 1 line in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (feat-runall@d1aa593). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/lib/pipeline/core/signal.rs	95.65%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##             feat-runall     #416   +/-   ##
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  Coverage               ?   93.31%           
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  Files                  ?      138           
  Lines                  ?    54928           
  Branches               ?        0           
==============================================
  Hits                   ?    51254           
  Misses                 ?     3674           
  Partials               ?        0           

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 1d296e52-aeea-44e2-ab7d-a7d0865841fe

📥 Commits

Reviewing files that changed from the base of the PR and between d1aa593 and 87ed834.

📒 Files selected for processing (3)

• src/lib/pipeline/core/builder.rs
• src/lib/pipeline/core/runtime/fused.rs
• src/lib/pipeline/core/signal.rs

📝 Walkthrough

Walkthrough

Adds PipelineError::reconstruct(&self) -> PipelineError to signal.rs, which rebuilds an owned PipelineError from a borrowed one—recreating the Io variant via io::Error::new(kind(), display_string) and copying other variants directly. Two call sites—Pipeline::run in builder.rs and run_fused_single_thread in fused.rs—drop their explicit per-variant match arms and the local PipelineError import in favor of a single err.reconstruct() call. A new unit test verifies round-trip fidelity for all four variants.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	Title accurately describes the main refactoring: extracting PipelineError::reconstruct to eliminate duplicated outcome matching logic across two call sites.
Description check	✅ Passed	Description clearly explains the refactoring's purpose, implementation approach, and behavior preservation; directly relates to the code changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

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• Create PR with unit tests
• Commit unit tests in branch feat-runall-22-pipeline-error-reconstruct

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