fix: BACKLOG_NUMS array in supervisor-poll.sh is never queried (#110)

The BACKLOG_NUMS associative array was built to track which issue numbers
are in the backlog, but the DFS cycle-detection code used NODE_COLOR as
a membership guard instead. This meant deps pointing to non-backlog issues
were only skipped by coincidence (they weren't in NODE_COLOR either).

Three changes:
- Remove SC2034 suppression since BACKLOG_NUMS is now actually queried
- Initialize NODE_COLOR from BACKLOG_NUMS keys (all backlog issues) instead
  of DEPS_OF keys (only issues with dependencies), so every backlog issue
  gets a proper DFS color
- Replace the NODE_COLOR membership check with BACKLOG_NUMS in the DFS, so
  the guard explicitly asks "is this dep a backlog issue?" rather than
  relying on NODE_COLOR initialization as a proxy

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

supervisor/supervisor-poll.sh

@@ -467,12 +467,11 @@ check_project() {
       BODY=$(echo "$BACKLOG_FOR_DEPS" | jq -r ".[$i].body // \"\"")
       ISSUE_DEPS=$(echo "$BODY" | bash "$PARSE_DEPS" | grep -v "^${NUM}$" || true)
       [ -n "$ISSUE_DEPS" ] && DEPS_OF[$NUM]="$ISSUE_DEPS"
-      # shellcheck disable=SC2034
       BACKLOG_NUMS[$NUM]=1
     done
 
     declare -A NODE_COLOR
-    for node in "${!DEPS_OF[@]}"; do NODE_COLOR[$node]=0; done
+    for node in "${!BACKLOG_NUMS[@]}"; do NODE_COLOR[$node]=0; done
 
     FOUND_CYCLES=""
     declare -A SEEN_CYCLES
@@ -481,7 +480,7 @@ check_project() {
       local node="$1" path="$2"
       NODE_COLOR[$node]=1
       for dep in ${DEPS_OF[$node]:-}; do
-        [ -z "${NODE_COLOR[$dep]+x}" ] && continue
+        [ -z "${BACKLOG_NUMS[$dep]+x}" ] && continue
         if [ "${NODE_COLOR[$dep]}" = "1" ]; then
           local cycle_key
               cycle_key=$(echo "$path $dep" | tr ' ' '\n' | sort -n | tr '\n' ' ')