feat: factory supervisor with priorities, auto-fix, and claude -p escalation

- P0: memory crisis (auto-kill stale claude, drop caches, restart Anvil)
- P1: disk pressure (docker prune, log truncate, worktree cleanup, WP log trim)
- P2: factory stopped (CI stuck, dev-agent dead, git broken — auto-fix where possible)
- P3: factory degraded (derailed PRs, auto-trigger reviews)
- P4: housekeeping (stale processes, log rotation)

Calls claude -p only for P0/P1 issues that auto-fix couldn't resolve.
PROMPT.md contains distilled operational knowledge + self-update mechanism.

factory/update-prompt.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# update-prompt.sh — Append a lesson learned to PROMPT.md
+#
+# Usage:
+#   ./factory/update-prompt.sh "### Title" "Body text describing the lesson"
+#   ./factory/update-prompt.sh --from-file /tmp/lesson.md
+#
+# Called by claude -p when it learns something new during a fix.
+# Commits and pushes the update to the dark-factory repo.
+
+source "$(dirname "$0")/../lib/env.sh"
+
+PROMPT_FILE="${FACTORY_ROOT}/factory/PROMPT.md"
+
+if [ "$1" = "--from-file" ] && [ -f "$2" ]; then
+  LESSON=$(cat "$2")
+elif [ -n "$1" ] && [ -n "$2" ]; then
+  LESSON="$1
+$2"
+else
+  echo "Usage: update-prompt.sh 'Title' 'Body' OR update-prompt.sh --from-file path" >&2
+  exit 1
+fi
+
+# Append to PROMPT.md under Best Practices
+echo "" >> "$PROMPT_FILE"
+echo "$LESSON" >> "$PROMPT_FILE"
+
+cd "$FACTORY_ROOT"
+git add factory/PROMPT.md
+git commit -m "factory: update supervisor best practices" --no-verify 2>/dev/null
+git push origin main 2>/dev/null
+
+log "PROMPT.md updated with new lesson"