v0.3.0 finish: TUI tests, embedding wiring, gateway :configured, focus commands, export cleanup

- TUI: Fix stale contract (remove handle-return/*incoming-msgs*), rewrite
  10->13 tests (38 checks, 100% pass). Export missing symbols from TUI
  package. Fix view-chat contract arity.
- Gateway messaging: Add :configured key to registry (boolean, nil default).
  Fix contract to match (vault-based, not env-var-based).
- Async Embedding Gateway: Add *embedding-backend* var, embeddings-compute
  function. Modify ingest-ast to populate vectors on new objects.
  Add EMBEDDING_PROVIDER env var support. Add Contract + 4 tests (8 checks).
- Context Manager: Add /focus, /scope, /unfocus commands to TUI on-key
  handler. Commands degrade gracefully when context-manager not loaded.
- Export hygiene: Remove 30+ ghost exports (undefined symbols). Remove
  duplicate/mismatched names. Exports now match actual definitions.

org/gateway-tui-model.org

@@ -22,7 +22,9 @@ All state mutation flows through event handlers in the controller.
   (:use :cl :croatoan :passepartout :usocket :bordeaux-threads)
   (:export :tui-main :st :add-msg :now :input-string
            :queue-event :drain-queue :init-state
-           :view-status :view-chat :view-input :redraw))
+           :view-status :view-chat :view-input :redraw
+           :on-key :on-daemon-msg :send-daemon
+           :connect-daemon :disconnect-daemon))
 (in-package :passepartout.gateway-tui)
 
 (defvar *state* nil)