Optimize dead-code-remover prompt to cut turn count and context growth

[Copilot]

The Dead Code Removal Agent was running ~57-turn executions with high cache amplification, primarily from fragmented safety checks, split verification commands, and verbose inline prompt content. This updates the workflow prompt to reduce per-run turns while preserving dead-code safety gates.

• Discovery moved to a small sub-agent

  • Replaced Phase 1/2 prose with an inline discover-candidates sub-agent contract.
  • Standardized stdout JSON shape for parent-agent consumption: skip + candidates.
  • Kept required exclusions for shared test helpers and cache-based dedupe behavior.

• Phase 4 safety checks collapsed to one bash block per function

  • Consolidated caller grep, WASM check, console_wasm check, and constant/embed scan into a single execution unit per candidate.
  • Added path normalization guidance and kept skip semantics for live non-test/WASM usages.

• Phase 6 verification chained + circuit breaker

  • Converted multi-block verification into one chained command flow.
  • Added explicit soft/hard turn-budget guidance with a >35-turn circuit breaker that skips go test and continues with reduced verification.

• PR body instructions compressed

  • Replaced the large inline PR template with a compact required-structure contract (functions table, tests section, verification checklist, run URL).

func="FunctionName"
file="pkg/path/file.go"
file="${file#./}"

echo "=== Caller check ==="
grep -rn -m 5 "$func" --include="*.go" .

if [[ "$file" == "pkg/workflow/"* || "$file" == "pkg/console/"* ]]; then
  echo "=== WASM check ==="
  grep -n "$func" cmd/gh-aw-wasm/main.go || true
fi

if [[ "$file" == "pkg/console/"* ]]; then
  echo "=== console_wasm check ==="
  grep -n "$func" pkg/console/console_wasm.go || true
fi