feat: add cross-run finding regression detection

lib/archeflow-memory.sh

@@ -11,6 +11,7 @@
 #   ./lib/archeflow-memory.sh list                        # List all active lessons
 #   ./lib/archeflow-memory.sh decay                       # Apply decay to all lessons
 #   ./lib/archeflow-memory.sh forget <id>                 # Archive a lesson by ID
+#   ./lib/archeflow-memory.sh regression-check <events>  # Detect regressions from previously fixed findings
 #
 # Dependencies: jq, bash 4+
 
@@ -361,6 +362,86 @@ cmd_audit_check() {
   done <<< "$lesson_ids"
 }
 
+cmd_regression_check() {
+  local events_file="${1:?Usage: $0 regression-check <events.jsonl>}"
+
+  if [[ ! -f "$events_file" ]]; then
+    echo "Error: events file not found: $events_file" >&2
+    exit 1
+  fi
+
+  # Extract current run_id
+  local run_id
+  run_id=$(jq -r '.run_id' "$events_file" | head -1)
+
+  # Find the previous run from index.jsonl
+  local INDEX_FILE=".archeflow/events/index.jsonl"
+  if [[ ! -f "$INDEX_FILE" ]]; then
+    echo "[archeflow-memory] No index.jsonl found — skipping regression check." >&2
+    return 0
+  fi
+
+  local prev_run_id
+  prev_run_id=$(jq -r --arg rid "$run_id" 'select(.run_id != $rid) | .run_id' "$INDEX_FILE" 2>/dev/null | tail -1)
+
+  if [[ -z "$prev_run_id" ]]; then
+    echo "[archeflow-memory] No previous run found — skipping regression check." >&2
+    return 0
+  fi
+
+  local prev_events=".archeflow/events/${prev_run_id}.jsonl"
+  if [[ ! -f "$prev_events" ]]; then
+    echo "[archeflow-memory] Previous run events not found: $prev_events" >&2
+    return 0
+  fi
+
+  # Extract resolved findings from previous run (fix.applied events)
+  local resolved_findings
+  resolved_findings=$(jq -r 'select(.type == "fix.applied") | .data.finding // empty' "$prev_events" 2>/dev/null || true)
+
+  if [[ -z "$resolved_findings" ]]; then
+    echo "[archeflow-memory] No resolved findings in previous run — nothing to regress." >&2
+    return 0
+  fi
+
+  # Extract current run findings from review.verdict events
+  local current_findings
+  current_findings=$(jq -r '
+    select(.type == "review.verdict") |
+    .data.findings[]? | .description // empty
+  ' "$events_file" 2>/dev/null || true)
+
+  if [[ -z "$current_findings" ]]; then
+    echo "[archeflow-memory] No findings in current run — no regressions." >&2
+    return 0
+  fi
+
+  # Compare: for each resolved finding, check if it reappeared
+  local regressions=0
+  while IFS= read -r resolved; do
+    [[ -z "$resolved" ]] && continue
+
+    while IFS= read -r current; do
+      [[ -z "$current" ]] && continue
+      local overlap
+      overlap=$(keyword_overlap "$resolved" "$current")
+      if [[ "$overlap" -ge 50 ]]; then
+        echo "REGRESSION: \"$resolved\" (fixed in $prev_run_id) reappeared as \"$current\""
+        regressions=$((regressions + 1))
+        break
+      fi
+    done <<< "$current_findings"
+  done <<< "$resolved_findings"
+
+  if [[ "$regressions" -gt 0 ]]; then
+    echo "[archeflow-memory] $regressions regression(s) detected from run $prev_run_id." >&2
+    return 1
+  else
+    echo "[archeflow-memory] No regressions detected." >&2
+    return 0
+  fi
+}
+
 cmd_add() {
   local type="${1:-preference}"
   local desc="${2:-}"
@@ -503,6 +584,7 @@ if [[ $# -lt 1 ]]; then
   echo "  decay                        Apply decay to all lessons" >&2
   echo "  forget <id>                  Archive a lesson by ID" >&2
   echo "  audit-check <run_id>         Check lesson effectiveness for a run" >&2
+  echo "  regression-check <events.jsonl>  Detect regressions from previously fixed findings" >&2
   exit 1
 fi
 
@@ -535,6 +617,10 @@ case "$COMMAND" in
     [[ $# -lt 1 ]] && { echo "Usage: $0 audit-check <run_id>" >&2; exit 1; }
     cmd_audit_check "$1"
     ;;
+  regression-check)
+    [[ $# -lt 1 ]] && { echo "Usage: $0 regression-check <events.jsonl>" >&2; exit 1; }
+    cmd_regression_check "$1"
+    ;;
   *)
     echo "Unknown command: $COMMAND" >&2
     exit 1