fix(overseer): evidence-collector skips target/ probe fixtures (#4449)

[rysweet]

Summary

Fixes the evidence-collector defect (#4449) that manufactured a false-positive stale-engineer reap of goal advance-rysweet-agent-kgpacks-rs-to-full-parity-f29bb15c.

collect_worktree_evidence (src/overseer/claim_reaper.rs) walked the entire engineer worktree skipping only .git. Cargo's target/operator-probe-state/** and target/test-state/** carry canned error_reflection.json fixtures. Rewritten every run, they sort NEWEST and evict the real transcript from the bounded MAX_FILES=8 window — so the stale-engineer investigator saw a bogus:

NOT_A_REPO: '/tmp/simard-engineer-loop-not-a-repo-1784855002338594603' is not inside a valid git worktree ... exit 128

as the apparent cause of death, when the real terminal session had completed cleanly (terminal-foundation-ok, COMMAND_EXIT_CODE=0, phase=complete, correct worktree cwd).

Fix

Skip the whole target/ subtree during evidence collection (mirrors the existing .git skip). The genuine engineer transcript always lives outside target/ (recipe-runner logs, .claude/runtime/, session state), so this is safe and cannot drop real evidence.

Test

Adds collect_worktree_evidence_skips_target_probe_fixtures: plants a target/operator-probe-state/.../error_reflection.json NOT_A_REPO fixture plus a real engineer-transcript.log, asserts the fixture is excluded and the real transcript is still collected. Both evidence-collector tests pass; cargo fmt + cargo clippy --release -D warnings pre-commit/pre-push gates green.

Grounding

Archived evidence: ~/.simard/reaped-engineers/rysweet_Simard_advance-rysweet-agent-kgpacks-rs-to-full-parity-f29bb15c-1784862545/ (manifest.json, evidence.txt line 157 + evidence-15, journal.txt). Investigation verdict: still-alive / false-positive; claim + worktree preserved (fail-closed). Related diagnostic-layer defect: #4500 (idle-age conflates completed with wedged).

Closes #4449

[github-actions]

📊 Coverage Summary

Generated by cargo llvm-cov --workspace --summary-only (nightly, excluding test files)

Module	Lines	Covered	Coverage
Total	196459	165207	84.1%

_{Coverage data from CI run. Test files matching tests?/ are excluded from line counts.}