readme: add core architecture diagram

README.md

@@ -184,6 +184,63 @@ See [doc/REMOTE_EXECUTION.md](doc/REMOTE_EXECUTION.md) for the design.
 
 ## Architecture
 
+```mermaid
+graph TB
+    subgraph Frontends
+        TER[Terminal<br>b / bfg / sh]
+        ACME[Plan 9 acme]
+        EMACS[Emacs<br>ellie.el]
+        KDE[KDE<br>plasmoid / GUI / Kate<br>KRunner / tray]
+        WEB[Web UI<br>Preact SPA]
+    end
+
+    subgraph "olliesrv"
+        9P[9P Filesystem]
+        DBUS[D-Bus Adapter]
+        SM[Session Manager]
+        CORE[Core Library<br>agent loop · compaction<br>prompt templates]
+        ROUTE[Router<br>complete · generate · route]
+        TOOLS[Tool Registry<br>lazy-load · dispatch]
+        SB[Landlock Sandbox]
+    end
+
+    subgraph "LLM Backends"
+        OLL[Ollama]
+        OAI[OpenAI / OpenRouter]
+        ANT[Anthropic]
+        COP[Copilot]
+        KIRO[Kiro]
+    end
+
+    subgraph Execution
+        LOCAL[Local Tools<br>file_read · lsp_* · shell<br>memory_* · gui_*]
+        REMOTE[ollie-remote<br>via SSH]
+        RTOOL[Remote Tools]
+    end
+
+    HTTPGW[ollie-httpgw<br>HTTP→9P gateway]
+
+    %% Frontend connections
+    TER & ACME & EMACS -->|9P| 9P
+    KDE -->|D-Bus| DBUS
+    WEB --> HTTPGW --> 9P
+
+    %% Internal layers
+    9P --> SM
+    DBUS --> SM
+    SM --> CORE
+    CORE --> ROUTE
+    CORE --> TOOLS
+    TOOLS --> SB
+
+    %% Backend connections
+    CORE -->|streaming| OLL & OAI & ANT & COP & KIRO
+
+    %% Tool execution
+    SB --> LOCAL
+    SB -->|SSH| REMOTE --> RTOOL
+```
+
 `olliesrv` is a single binary that operates in three modes:
 
 | Mode | Flags | Interface | Frontends |