swarm: Rule 4 — engram-write is @manager-ONLY, enforced by capability

New hard invariant (Will): only the orchestrator mutates global engram state;
workers are read-only against the full engram + write only their own local
geometry. This is an AUTHORITY gate (capability), not a health gate — a worker
is STRUCTURALLY UNABLE to mutate global engram state regardless of engram health.

- containment.el: scope tokens now carry a caps set. Orchestrator token holds
  engram:write + dharma:emit (@manager-only, the VBD rule that only the manager
  mutates global state); worker token holds ONLY engram:read. Rule 4:
  containment_check_engram_write / _dharma_emit reject any caller lacking the
  capability — same scope-token mechanism as the live Rule-2 denial.
- swarm.el: swarm_engram_write is the ONLY engram write path, gated by Rule 4;
  a worker token is denied before any HTTP is issued (no mutation). The curated
  merge (commit=1) is the sole writer: the orchestrator commits approved
  geometry via its write-capable token. Workers' full-engram READ stays intact.
- reshape_surface.el: compose op_write (json_escape_string) for the commit path.
- harness: Rule-4 suite proven — worker engram-write DENIED by capability, no
  node created, violation journalled; orchestrator passes the gate as sole
  writer. 24/24 green on the :8901 clone with real cognition.

Authority gate holds independent of daemon write-health (proven with daemon
both alive and, earlier, crashed). Prod :8742 untouched.

lang/swarm/tests/harness_real_cognition.el

@@ -76,6 +76,39 @@ fn main() -> Int {
     let completed: Int = worktrack_count_kind(corr, "worker.completed")
     let fails = ok("work-tracking: 8 started + 8 completed", (started == 8) && (completed == 8), fails)
 
+    // ── G) RULE 4 — engram-write is @manager-ONLY (authority gate) ──
+    // A worker token (engram:read only) is STRUCTURALLY denied any engram write.
+    let worker_tok: String = containment_worker_token(corr, corr + "/worker-1")
+    let orch_tok: String = containment_coordinator_token(corr)
+    let fails = ok("worker token carries engram:read", containment_has_cap(worker_tok, "engram:read"), fails)
+    let fails = ok("worker token does NOT carry engram:write", !containment_has_cap(worker_tok, "engram:write"), fails)
+    let fails = ok("orchestrator token carries engram:write", containment_has_cap(orch_tok, "engram:write"), fails)
+    // a worker attempting an engram write is DENIED BY CAPABILITY (no HTTP issued)
+    let wdeny: String = swarm_engram_write(worker_tok, corr, "worker tries to mutate global state", "memory", 0.5)
+    let denied_reason: String = json_get_string(wdeny, "denied")
+    let fails = ok("worker engram-write DENIED by capability (Rule 4)", str_contains(denied_reason, "rule 4"), fails)
+    let fails = ok("denied worker write performed NO engram mutation (no node id)", str_eq(json_get_string(wdeny, "id"), ""), fails)
+    let fails = ok("Rule-4 violation journalled", worktrack_count_kind(corr, "containment.violation") >= 1, fails)
+    // the orchestrator passes the capability gate (sole authorized writer)
+    let odeny: String = containment_check_engram_write(orch_tok, "engram.write")
+    let fails = ok("orchestrator PASSES the engram-write capability gate (sole writer)", str_eq(odeny, ""), fails)
+
+    // ── H) curated merge = the only write path (orchestrator commits) ──
+    // The AUTHORITY gate above is already proven (worker denied, orchestrator
+    // authorized) WITHOUT issuing a write. The actual persisting commit exercises
+    // the engram write path, which needs the gate-1 write-healthy clone — so it
+    // runs only under SWARM_WRITE_HEALTHY=1 (else it would hit the known daemon
+    // write-crash). Authority != health: the gate holds either way.
+    if str_eq(env("SWARM_WRITE_HEALTHY"), "1") {
+        let cfg_commit: String = "{\"concurrency\":\"4\",\"strategy\":\"reduce\",\"min_success_ratio\":\"1.0\",\"commit\":\"1\"}"
+        let rc: String = swarm_run("cognize", refs, anchors, cfg_commit)
+        let committed: String = json_get_string(rc, "committed_node")
+        let fails2: Int = ok("orchestrator (sole writer) committed the merge to the engram", !str_eq(committed, ""), fails)
+        let fails = fails2
+    } else {
+        print("  note  curated-merge commit deferred to the gate-1 write-healthy clone (set SWARM_WRITE_HEALTHY=1); authority gate already proven above")
+    }
+
     print("")
     if fails == 0 {
         print("REAL-COGNITION SWARM GREEN — Neuron thinking in parallel over its own geometry.")