[JacobStephens2]

Summary

Failed Harness sessions keep recoverable usage and warnings while preserving the original transport error.

Session → Harness process streaming(state, consume)
            run child and concurrent I/O
            complete or clean up; join every worker
            return Streamed { execution, state }
        → state.finish(execution)
            report once; propagate the original transport failure

The process module now owns recovery after every normal consumer return. Session uses the returned interpretation directly; interruption suppresses recovery and completion reporting.

Closes #461

Evidence

• Before: completed_stdout_is_reported_after_a_broken_prompt failed with left: 0, right: 1 for the missing-skill warning. Successful stdout consumption followed by BrokenPipe lost retained export, usage and completion reporting.
  After: the regression passes with the original BrokenPipe cause, the exact child PID reaped, one retained export, one warning, one usage summary and one session-ended line.
• Additional fixtures cover partial consumption and log failure with a blocked prompt, error precedence during cleanup, consumer panic, startup failure and interruption. Existing byte-preservation, EOF/exit ordering, captured-stderr, detached-descendant and Resume regressions pass.
• Validation: cargo check --all-targets, cargo fmt --check, cargo clippy --all-targets -- -D warnings, and cargo test (1,240 tests passed).

Seams under test:

• Harness process streaming: recovered state, execution errors, owned cleanup and worker completion.
• Session execution (Sessions::within / run_to_final_message) with local shell CLI fixtures: retained reads, reporting, interruption and Resume eligibility.

Merge Danger

Door: two-way

The internal interface change can be reverted without a data migration.

Blast Radius: Sessions

Harness session execution and completion reporting across all six Harnesses.

Unaddressed findings

Standards

None. Review against main reported no findings.

Spec

None. Review against #461 reported no findings.

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