docs: update architecture diagram, fix ellie.el for ctl rdwr

README: mermaid diagram now shows o CLI as the foundation layer
between text frontends and 9P. KDE/Kate connect directly to 9P.

ellie.el (both versions): add ellie--9p-rdwr wrapper, use ctl rdwr
for systemprompt (no longer a standalone file).

README.md

@@ -94,16 +94,23 @@ Single Go module with one Git submodule (kde).
 
 ```mermaid
 graph TB
-    subgraph Frontends
-        ACME[Plan 9 acme]
+    subgraph "Frontends (all use o / ollie-9p)"
+        TUI["o tui<br>(tmux + o read/ctl)"]
+        KDE[KDE GUI<br>ollie-9p native client]
+        KATE[Kate plugin]
         EMACS[Emacs<br>ellie.el]
-        KDE[KDE<br>GUI / Kate / KRunner]
+        ACME[Plan 9 acme]
+        SCRIPTS[Shell scripts<br>o read · o ctl · o write]
+    end
+
+    subgraph "o CLI"
+        O["o<br>path resolution · ctl dispatch<br>prompt REPL · TUI composition"]
     end
 
     subgraph "olliesrv"
         P9[9P Filesystem<br>session/ namespace]
         SM[Session Manager]
-        AG[agent.Agent<br>loop · compaction<br>prompt templates]
+        AG[agent.Agent<br>loop · compaction<br>prompt assembly]
         ROUTE[Router<br>complete · generate · route]
         TOOLS[toolsrv.Server<br>dynamic dispatch · sandbox]
     end
@@ -121,7 +128,9 @@ graph TB
         REMOTE[ollie-remote<br>via SSH · no embedded tools]
     end
 
-    ACME & EMACS & KDE --> P9
+    TUI & SCRIPTS & EMACS & ACME --> O
+    O --> P9
+    KDE & KATE --> P9
     P9 --> SM
     SM --> AG
     AG --> ROUTE
@@ -134,7 +143,9 @@ graph TB
 ```
 
 `olliesrv` exposes the agent runtime over a single surface: a 9P2000 filesystem.
-KDE GUI, Kate plugin, and KRunner all use 9P internally. For a deep dive into the
+`o` is the CLI layer that all text-based frontends build on — it handles path
+resolution, context, and ctl dispatch. The KDE GUI and Kate plugin use `ollie-9p`
+(the native 9P client) directly for performance. For a deep dive into the
 filesystem, see [`doc/resources/9p.md`](doc/resources/9p.md).
 
 ## Credits

contrib/elisp/el/ellie.el

@@ -106,6 +106,18 @@ Returns nil on any error."
       (unless (zerop rc)
         (user-error "ollie-9p write %s failed (exit %d)" path rc)))))
 
+(defun ellie--9p-rdwr (path text)
+  "Write TEXT to PATH via ollie-9p rdwr and return the response.
+Returns nil on any error."
+  (condition-case nil
+      (with-temp-buffer
+        (insert text)
+        (if (= (call-process-region (point-min) (point-max)
+                                    "ollie-9p" t t nil "rdwr" path) 0)
+            (buffer-string)
+          nil))
+    (error nil)))
+
 (defun ellie--9p-ls (path)
   "Return list of entry names under PATH via ollie-9p ls.
 Returns nil on error."
@@ -496,8 +508,8 @@ Key bindings:
 (defun ellie-show-system-prompt ()
   "Display the rendered system prompt for the current session in a buffer."
   (interactive)
-  (let* ((path (ellie--session-file "systemprompt"))
-         (text (ellie--9p-read path)))
+  (let* ((path (ellie--session-file "ctl"))
+         (text (ellie--9p-rdwr path "systemprompt")))
     (unless text
       (user-error "Could not read system prompt"))
     (let ((buf (get-buffer-create "*ellie-system-prompt*")))

contrib/elisp/ellie.el

@@ -89,6 +89,18 @@ Returns nil on any error."
       (unless (zerop rc)
         (user-error "ollie-9p write %s failed (exit %d)" path rc)))))
 
+(defun ellie--9p-rdwr (path text)
+  "Write TEXT to PATH via ollie-9p rdwr and return the response.
+Returns nil on any error."
+  (condition-case nil
+      (with-temp-buffer
+        (insert text)
+        (if (= (call-process-region (point-min) (point-max)
+                                    "ollie-9p" t t nil "rdwr" path) 0)
+            (buffer-string)
+          nil))
+    (error nil)))
+
 (defun ellie--9p-ls (path)
   "Return list of entry names under PATH via ollie-9p ls.
 Returns nil on error."
@@ -744,8 +756,8 @@ QUEUED non-nil means the prompt will be enqueued, not submitted immediately."
 (defun ellie-show-system-prompt ()
   "Display the rendered system prompt for the current agent."
   (interactive)
-  (let* ((path (ellie--session-file "systemprompt"))
-         (text (ellie--9p-read path)))
+  (let* ((path (ellie--session-file "ctl"))
+         (text (ellie--9p-rdwr path "systemprompt")))
     (unless text
       (user-error "Could not read system prompt"))
     (let ((buf (get-buffer-create "*ellie-system-prompt*")))