feat(issue-261): build workspace stale-test audit lane

[graysurf]

Summary

• Implements Sprint 1 lane tasks S1T1-S1T4 for issue Plan: Workspace obsolete test cleanup and de-risking #261 by adding a deterministic workspace stale-test audit workflow.
• Adds normalized stale-test inventory output plus helper callgraph/orphan analysis, contract protection allowlist, tier assignments, and execution manifest artifacts under $AGENT_HOME/out/workspace-test-cleanup.

Scope

• Added scripts/dev/workspace-test-stale-audit.sh with deterministic full-workspace scanning and normalized schema output (id, crate, path, symbol_or_test, signal, proposed_action, confidence).
• Implemented Task 1.2 outputs: helper-callgraph.tsv and helper-orphans.tsv with deterministic IDs and manual-review flags for macro/reflection edge patterns.
• Implemented Task 1.3 outputs: decision-rubric.md and contract-allowlist.tsv with explicit remove|keep|rewrite|defer rules and contract/parity/json/exit-code protections.
• Implemented Task 1.4 outputs: crate-tiers.tsv (candidate-tier-task assignment) and execution-manifest.md (serialized high-overlap crates + lane gating).
• Excluded: Sprint 2+ code cleanup tasks (helper deletion/refactors) and any non-lane runtime behavior changes.

Testing

• bash -n scripts/dev/workspace-test-stale-audit.sh (pass)
• mkdir -p "$AGENT_HOME/out/workspace-test-cleanup" (pass)
• bash scripts/dev/workspace-test-stale-audit.sh --format tsv --out "$AGENT_HOME/out/workspace-test-cleanup/stale-tests.tsv" (pass)
• cp "$AGENT_HOME/out/workspace-test-cleanup/stale-tests.tsv" "$AGENT_HOME/out/workspace-test-cleanup/stale-tests.r1.tsv" (pass)
• bash scripts/dev/workspace-test-stale-audit.sh --format tsv --out "$AGENT_HOME/out/workspace-test-cleanup/stale-tests.r2.tsv" (pass)
• diff -u "$AGENT_HOME/out/workspace-test-cleanup/stale-tests.r1.tsv" "$AGENT_HOME/out/workspace-test-cleanup/stale-tests.r2.tsv" (pass)
• test -s "$AGENT_HOME/out/workspace-test-cleanup/helper-callgraph.tsv" (pass)
• test -s "$AGENT_HOME/out/workspace-test-cleanup/helper-orphans.tsv" (pass)
• awk -F '\t' 'NR>1 && $4=="0" {print $1}' "$AGENT_HOME/out/workspace-test-cleanup/helper-callgraph.tsv" | sort > "$AGENT_HOME/out/workspace-test-cleanup/orphans-from-callgraph.ids" (pass)
• awk -F '\t' 'NR>1 {print $1}' "$AGENT_HOME/out/workspace-test-cleanup/helper-orphans.tsv" | sort > "$AGENT_HOME/out/workspace-test-cleanup/orphans-reported.ids" (pass)
• diff -u "$AGENT_HOME/out/workspace-test-cleanup/orphans-from-callgraph.ids" "$AGENT_HOME/out/workspace-test-cleanup/orphans-reported.ids" (pass)
• test -s "$AGENT_HOME/out/workspace-test-cleanup/decision-rubric.md" (pass)
• test -s "$AGENT_HOME/out/workspace-test-cleanup/contract-allowlist.tsv" (pass)
• rg -n 'remove|keep|rewrite|defer|contract|parity|exit code|json' "$AGENT_HOME/out/workspace-test-cleanup/decision-rubric.md" (pass)
• test -s "$AGENT_HOME/out/workspace-test-cleanup/execution-manifest.md" (pass)
• test -s "$AGENT_HOME/out/workspace-test-cleanup/crate-tiers.tsv" (pass)
• awk -F '\t' 'NR>1 && ($2=="" || $3=="" || $4=="") {print $0}' "$AGENT_HOME/out/workspace-test-cleanup/crate-tiers.tsv" | wc -l | tr -d ' ' | rg '^0$' (pass)
• plan-tooling validate --file /Users/terry/Project/graysurf/nils-cli/docs/plans/workspace-obsolete-tests-cleanup-plan.md (pass)
• ./.agents/skills/nils-cli-verify-required-checks/scripts/nils-cli-verify-required-checks.sh (pass)
• cargo llvm-cov nextest --profile ci --workspace --lcov --output-path target/coverage/lcov.info --fail-under-lines 85 (fail: transient SIGKILL during test listing)
• CARGO_BUILD_JOBS=4 NEXTEST_TEST_THREADS=1 cargo llvm-cov nextest --profile ci --workspace --lcov --output-path target/coverage/lcov.info --fail-under-lines 85 (pass)
• scripts/ci/coverage-summary.sh target/coverage/lcov.info (pass; Total line coverage 86.47%)

Issue

• Plan: Workspace obsolete test cleanup and de-risking #261

[github-actions]

Coverage

Total line coverage: 86.44% (58946/68195 lines hit).