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-messaging.org

@@ -20,7 +20,7 @@ This replaces the old ~gateway-manager~ skill. The Telegram/Signal platform code
 ** Contract
 
 1. (gateway-registry-initialize): populates ~*gateway-registry*~ with
-   ~:configured~ status per platform based on env vars.
+   ~:configured~ key per platform (boolean, set when linked).
 2. (messaging-link platform &key token): stores the token in the vault
    and starts the gateway's polling thread.
 3. (messaging-unlink platform): removes the token and stops the thread.
@@ -142,11 +142,13 @@ This replaces the old ~gateway-manager~ skill. The Telegram/Signal platform code
   (setf (gethash "telegram" *gateway-registry*)
         (list :poll-fn #'telegram-poll
               :send-fn #'telegram-send
-              :default-interval 3))
+              :default-interval 3
+              :configured nil))
   (setf (gethash "signal" *gateway-registry*)
         (list :poll-fn #'signal-poll
               :send-fn #'signal-send
-              :default-interval 5)))
+              :default-interval 5
+              :configured nil)))
 
 (defun gateway-configured-p (platform)
   "Returns T if a platform has a stored token."
@@ -292,9 +294,14 @@ This replaces the old ~gateway-manager~ skill. The Telegram/Signal platform code
 (in-suite messaging-suite)
 
 (test test-gateway-registry-initialize
-  "Contract 1: gateway-registry-initialize populates the registry."
+  "Contract 1: gateway-registry-initialize populates the registry with :configured key."
   (clrhash passepartout::*gateway-registry*)
   (gateway-registry-initialize)
   (is (not (zerop (hash-table-count passepartout::*gateway-registry*))))
-  (is (getf (gethash "telegram" passepartout::*gateway-registry*) :configured)))
+  (let ((entry (gethash "telegram" passepartout::*gateway-registry*)))
+    (is (getf entry :poll-fn))
+    (is (getf entry :send-fn))
+    (is (getf entry :default-interval))
+    ;; :configured key exists and is boolean (nil by default until linked)
+    (is (eq nil (getf entry :configured)))))
 #+end_src