feat(security): receipt admin scripts + user git-ops (zero exceptions)

Wire the remaining shell egress through gstack-egress-lib.sh:

- gstack-gbrain-mcp-verify: both JSON-RPC probe POSTs (initialize +
  tools/list) receipted fail-closed via payload files (hash == wire
  bytes). A refused receipt lands in the NETWORK class — no send.
- gstack-security-dashboard / gstack-community-dashboard: the
  community-pulse GETs receipted fail-open (read-only stats must not
  break over an audit hiccup).
- gstack-gbrain-supabase-provision: api_call receipted fail-closed.
  Each retry attempt hands the helper a fresh copy of the body file
  (the helper consumes its payload). The receipt hashes the request
  body only — the PAT never reaches the ledger or any log. Refusal
  exits 8 without retrying.
- git-class sha256:null receipts, fail-open: gstack-artifacts-init
  (ls-remote, initial push, fetch/pull recovery, retry push),
  gstack-brain-restore (staging clone, existing-repo fetch),
  gstack-session-update (self-update pull).

gstack-team-init needs no wiring: every git clone in it is inside an
echoed instruction string, not an executed command.

The lib now self-locates with shell builtins only (no dirname), so
sourcing works under the whitelist-PATH test harnesses.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
(cherry picked from commit b8c5e2055b21ab72878b3e46f8047782ee65a11c)

bin/gstack-session-update

@@ -11,6 +11,10 @@ set +e
 
 GSTACK_DIR="${GSTACK_DIR:-$HOME/.claude/skills/gstack}"
 STATE_DIR="${GSTACK_STATE_DIR:-$HOME/.gstack}"
+
+# Egress receipt helpers (_receipted_git): fail-open — an update pull must
+# never block a session over a receipt hiccup.
+. "$(cd "$(dirname "$0")" && pwd)/gstack-egress-lib.sh"
 THROTTLE_FILE="$STATE_DIR/.last-session-update"
 LOCK_DIR="$STATE_DIR/.setup-lock"
 LOG_FILE="$STATE_DIR/analytics/session-update.log"
@@ -76,7 +80,10 @@ fi
 
   # ── Pull latest ──
   OLD_HEAD=$(git -C "$GSTACK_DIR" rev-parse HEAD 2>/dev/null)
-  git -C "$GSTACK_DIR" pull --ff-only -q 2>/dev/null
+  UPDATE_URL=$(git -C "$GSTACK_DIR" remote get-url origin 2>/dev/null || echo "")
+  UPDATE_HOST="${UPDATE_URL#*://}"; UPDATE_HOST="${UPDATE_HOST#*@}"; UPDATE_HOST="${UPDATE_HOST%%[/:]*}"
+  GSTACK_HOME="$STATE_DIR" _receipted_git open session-update "${UPDATE_HOST:-unknown}" gstack-self-update-pull "auto_upgrade=true" \
+    bash -c 'git -C "$1" pull --ff-only -q 2>/dev/null' _ "$GSTACK_DIR"
   PULL_EXIT=$?
   NEW_HEAD=$(git -C "$GSTACK_DIR" rev-parse HEAD 2>/dev/null)