fix(framework): per-session ticket files unblock parallel sessions [#439]

The ticket gate required the single .crush/active-ticket file, so two
concurrent sessions overwrote each other's ticket mid-work. The gate now
accepts any non-empty .crush/active-ticket* file; each session keeps its
own (e.g. active-ticket-plant, active-ticket-core). Also prune .crush/
session scratch from both shellcheck scanners so one session's throwaway
probe scripts cannot block the other session's commits. Documented in
AGENTS.md Task Tracking.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

hooks/ticket-gate.sh

@@ -9,7 +9,6 @@
 # run audits, check status, etc.).
 set -euo pipefail
 
-TICKET_FILE="${CRUSH_PROJECT_DIR}/.crush/active-ticket"
 TOOL="${CRUSH_TOOL_NAME:-}"
 CMD="${CRUSH_TOOL_INPUT_COMMAND:-}"
 
@@ -54,12 +53,18 @@ case "$FILE_PATH" in
     ;;
 esac
 
-# Check for active ticket
-if [ -f "$TICKET_FILE" ] && [ -s "$TICKET_FILE" ]; then
-  TICKET=$(cat "$TICKET_FILE")
-  printf '{"context":"Active ticket: %s"}\n' "$TICKET"
-  exit 0
-fi
+# Check for active ticket. Parallel sessions each use their OWN file:
+#   .crush/active-ticket           (default / single session)
+#   .crush/active-ticket-<name>    (suffixed per session; any non-empty one
+#                                   satisfies the gate — sessions never fight
+#                                   over one file)
+GATE_OK=0
+for f in "$CRUSH_PROJECT_DIR"/.crush/active-ticket*; do
+  [ -f "$f" ] && [ -s "$f" ] || continue
+  GATE_OK=1
+  printf '{"context":"Active ticket(s): %s -> %s"}\n' "$(basename "$f")" "$(cat "$f")"
+done
+[ "$GATE_OK" -eq 1 ] && exit 0
 
 # No active ticket — block
 cat >&2 <<'MSG'