fix: fix: duplicated memory guard — memory_guard() in env.sh vs check_memory() in formula-session.sh (#279)

Remove check_memory() from lib/formula-session.sh and update all *-run.sh scripts
to use memory_guard() from lib/env.sh.

Changes:
- lib/formula-session.sh: Removed check_memory() function and its documentation
- gardener/gardener-run.sh: Replaced check_memory(2000) with memory_guard(2000)
- planner/planner-run.sh: Replaced check_memory(2000) with memory_guard(2000)
- architect/architect-run.sh: Replaced check_memory(2000) with memory_guard(2000)
- predictor/predictor-run.sh: Replaced check_memory(2000) with memory_guard(2000)
- supervisor/supervisor-run.sh: Replaced check_memory(2000) with memory_guard(2000)

Benefits:
- Only one memory check function exists now
- All agents use the same function
- No dependency on free command - uses /proc/meminfo which is more portable

lib/formula-session.sh

@@ -6,7 +6,6 @@
 #
 # Functions:
 #   acquire_cron_lock   LOCK_FILE          — PID lock with stale cleanup
-#   check_memory        [MIN_MB]           — skip if available RAM too low
 #   load_formula        FORMULA_FILE       — sets FORMULA_CONTENT
 #   build_context_block FILE [FILE ...]    — sets CONTEXT_BLOCK
 #   build_prompt_footer [EXTRA_API_LINES]  — sets PROMPT_FOOTER (API ref + env)
@@ -51,23 +50,6 @@ acquire_cron_lock() {
   trap 'rm -f "$_CRON_LOCK_FILE"' EXIT
 }
 
-# check_memory [MIN_MB]
-# Exits 0 (skip) if available memory is below MIN_MB (default 2000).
-check_memory() {
-  local min_mb="${1:-2000}"
-  # Graceful fallback if free command is not available (procps not installed)
-  if ! command -v free &>/dev/null; then
-    log "run: free not found, skipping memory check"
-    return 0
-  fi
-  local avail_mb
-  avail_mb=$(free -m | awk '/Mem:/{print $7}')
-  if [ "${avail_mb:-0}" -lt "$min_mb" ]; then
-    log "run: skipping — only ${avail_mb}MB available (need ${min_mb})"
-    exit 0
-  fi
-}
-
 # ── Agent identity resolution ────────────────────────────────────────────
 
 # resolve_agent_identity