feat(tess): add roster-bound tmux fleet provider

docs/tess/ARCHITECTURE.md

@@ -64,6 +64,12 @@ Valkey may hold ephemeral coordination state; PostgreSQL is canonical for durabl
 - **Forward:** Matrix/native Mosaic provider using authenticated identity, idempotent transaction IDs, replay cursors, and the same contract suite.
 - Discord/CLI never call tmux or Matrix directly.
 
+### Fleet/tmux Provider Boundary
+
+`TmuxFleetRuntimeProvider` supports only rostered fleet peers. Its transport resolves the configured roster socket itself and verifies the exact `=<agent>:0.0` pane and declared runtime command before every attach, message, or termination operation. Prefixes, unrostered session IDs, unavailable sockets, dead panes, and runtime identity mismatches fail closed; callers cannot supply a socket or raw tmux target.
+
+The provider advertises list, tree, read-only attach, send, and terminate. List/tree/health and read attach all default-deny until a scope-aware read authority permits the operation and exact peer. Attach produces a short-lived handle bound to the immutable actor, tenant, channel, and correlation scope; it never opens a server-side terminal and rejects `control` mode. Fleet stream support is intentionally absent. Tess has no direct write/control authority: send and terminate default-deny until a Mos authority adapter explicitly allows the exact session and immutable scope. The gateway registry remains the audit boundary for every requested, denied, and successful provider operation, and still consumes the exact-action termination approval before the provider is invoked.
+
 ## Plugin Families
 
 1. Channel: Discord now; other channels later.