fix(pier): widen returning identities, warm the Redis store, end stateless listen streams, refuse personal tokens without a TokenID

- Identity.fingerprint covers scopes, both subjects, the ceiling and the
  token kind; a stateful lookup or stateless hit whose fingerprint changed
  re-filters the server with the event diff under its own mutex (A-WR-04)
- Mount warms a Redis store in the background with a 1 s to 30 s backoff
  and every request kicks a pending open without waiting, so stateless-only
  instances subscribe to fan-out (A-WR-05)
- a stateless subscriptions/listen POST re-verifies its bearer every
  recheck interval; an LRU-evicted stateless server closes its sessions
  (A-WR-06)
- resolvePersonalToken refuses a subject with TokenID 0, and the
  pact.MCPPersonalTokenResolver contract says one resolver per application,
  false means unauthorized and TokenID keys the binding (A-WR-09, A-IN-03)

modules/pier/session.go

@@ -33,6 +33,7 @@ const (
 	methodListPrompts     = "prompts/list"
 	methodGetPrompt       = "prompts/get"
 	methodDiscover        = "server/discover"
+	methodListen          = "subscriptions/listen"
 )
 
 // ephemeralSession is the session value of the audit line of a tool call
@@ -64,10 +65,11 @@ type localSession struct {
 	transport *mcp.StreamableServerTransport
 	ss        *mcp.ServerSession
 
-	mu       sync.Mutex
-	identity Identity
-	tools    map[string]bool
-	prompts  map[string]bool
+	mu          sync.Mutex
+	identity    Identity
+	fingerprint string // of the identity the tool set was last filtered for
+	tools       map[string]bool
+	prompts     map[string]bool
 
 	initialized atomic.Bool
 	persisted   atomic.Bool
@@ -329,6 +331,7 @@ func (sr *sessionRouter) lookup(w http.ResponseWriter, r *http.Request, id Ident
 	}
 	ls.mu.Lock()
 	ls.identity = id
+	sr.p.widen(ctx, ls.server, id, &ls.fingerprint, ls.tools, ls.prompts)
 	ls.mu.Unlock()
 	if err := sr.p.store.Touch(ctx, sid, sr.p.cfg.IdleTTL); err != nil {
 		sr.p.storeUnavailable(w, err)
@@ -341,7 +344,7 @@ func (sr *sessionRouter) lookup(w http.ResponseWriter, r *http.Request, id Ident
 // with the session id, from the stored state when rehydrating. A goroutine
 // drops the local entry when the session closes.
 func (sr *sessionRouter) connect(ctx context.Context, sid string, id Identity, state *mcp.ServerSessionState) (*localSession, error) {
-	ls := &localSession{id: sid, binding: id.Binding, created: time.Now().UTC(), identity: id}
+	ls := &localSession{id: sid, binding: id.Binding, created: time.Now().UTC(), identity: id, fingerprint: id.fingerprint()}
 	srv, tools, prompts := sr.p.newServer(ctx, id, func() { ls.initialized.Store(true) })
 	ls.server, ls.tools, ls.prompts = srv, tools, prompts
 	ls.transport = &mcp.StreamableServerTransport{SessionID: sid}