fix: Extract memory_guard() to lib/env.sh to deduplicate poll scripts

The memory guard block in action-poll.sh and dev-poll.sh became
identical after removing matrix_send calls, triggering the
duplicate-detection CI check. Extract to a shared function in
lib/env.sh (already sourced by both scripts).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

action/action-poll.sh

@@ -25,11 +25,7 @@ log() {
 }
 
 # --- Memory guard ---
-AVAIL_MB=$(awk '/MemAvailable/{printf "%d", $2/1024}' /proc/meminfo)
-if [ "$AVAIL_MB" -lt 2000 ]; then
-  log "SKIP: only ${AVAIL_MB}MB available (need 2000MB)"
-  exit 0
-fi
+memory_guard 2000
 
 # --- Find open 'action' issues ---
 log "scanning for open action issues"

dev/dev-poll.sh

@@ -309,11 +309,7 @@ if [ -f "$LOCKFILE" ]; then
 fi
 
 # --- Memory guard ---
-AVAIL_MB=$(awk '/MemAvailable/{printf "%d", $2/1024}' /proc/meminfo)
-if [ "$AVAIL_MB" -lt 2000 ]; then
-  log "SKIP: only ${AVAIL_MB}MB available (need 2000MB)"
-  exit 0
-fi
+memory_guard 2000
 
 # =============================================================================
 # HELPER: check if a dependency issue is fully resolved (closed + PR merged)

lib/env.sh

@@ -146,6 +146,18 @@ wpdb() {
     -t "$@" 2>/dev/null
 }
 
+# Memory guard — exit 0 (skip) if available RAM is below MIN_MB.
+# Usage: memory_guard [MIN_MB]   (default 2000)
+memory_guard() {
+  local min_mb="${1:-2000}"
+  local avail_mb
+  avail_mb=$(awk '/MemAvailable/{printf "%d", $2/1024}' /proc/meminfo)
+  if [ "${avail_mb:-0}" -lt "$min_mb" ]; then
+    log "SKIP: only ${avail_mb}MB available (need ${min_mb}MB)"
+    exit 0
+  fi
+}
+
 # Source tea helpers (available when tea binary is installed)
 if command -v tea &>/dev/null; then
   # shellcheck source=tea-helpers.sh