v0.3.0 deferred: tab completion, multi-line, /help, activity indicator, context persistence, theming

- Tab completion: Tab key autocompletes / commands (Tab handler in on-key)
- Multi-line input: backslash + Enter inserts literal newline instead of sending
- /help command: displays full command listing with descriptions
- Activity indicator: :busy flag shows "...thinking" in status bar during LLM wait
- Context persistence: context-save/context-load persist *context-stack* to disk
  (~/.cache/passepartout/context.lisp). Auto-restores on skill load.
  Added push-context, pop-context, focus-*, unfocus, context-save/load exports.
- Theming: *tui-theme* plist with semantic color roles, /theme command
  View functions (view-chat, view-status, view-input) use theme-color
- TUI test suite: 19 tests, 53 checks (100% pass)
- Context test suite: 2 tests, 6 checks (100% pass)
- Total: 5 suites, 81 checks, 0 failures

org/gateway-tui-model.org

@@ -9,7 +9,7 @@ All state mutation flows through event handlers in the controller.
 ** Contract
 
 1. (init-state): returns a fresh state plist with ~:msgs~ list,
-   ~:input~ buffer, ~:dirty~ flag, and ~:connection~ status.
+   ~:input~ buffer, ~:dirty~ flag, ~:busy~ flag, and ~:connection~ status.
 2. (add-msg type text): appends a message to the ~:msgs~ list in
    ~*state*~, tagged with a timestamp and type. Truncates at the
    message buffer limit.
@@ -24,13 +24,23 @@ All state mutation flows through event handlers in the controller.
            :queue-event :drain-queue :init-state
            :view-status :view-chat :view-input :redraw
            :on-key :on-daemon-msg :send-daemon
-           :connect-daemon :disconnect-daemon))
+           :connect-daemon :disconnect-daemon
+           :*tui-theme* :theme-color))
 (in-package :passepartout.gateway-tui)
 
 (defvar *state* nil)
 (defvar *event-queue* nil)
 (defvar *event-lock* (bt:make-lock "tui-event-lock"))
 
+(defvar *tui-theme*
+  '(:user :green :agent :white :system :yellow :input :cyan
+    :connected :green :disconnected :red :timestamp :yellow)
+  "Color theme plist. Keys are semantic roles, values are Croatoan colors.")
+
+(defun theme-color (role)
+  "Returns the Croatoan color for a semantic role."
+  (or (getf *tui-theme* role) :white))
+
 (defun st (key) (getf *state* key))
 (defun (setf st) (val key) (setf (getf *state* key) val))
 
@@ -38,7 +48,8 @@ All state mutation flows through event handlers in the controller.
   (setf *state*
         (list :running t :mode :chat :connected nil :stream nil
               :input-buffer nil :input-history nil :input-hpos 0
-              :messages nil :scroll-offset 0 :dirty (list nil nil nil))))
+              :messages nil :scroll-offset 0 :busy nil
+              :dirty (list nil nil nil))))
 #+end_src
 
 ** Helpers