docs: add mermaid architecture diagram

Author: nooneknowspeter

docs/ARCHITECTURE.md

@@ -0,0 +1,62 @@
+# Architecutre
+
+```mermaid
+flowchart LR
+    user((user))
+
+
+    stdout
+    stdin
+    stderr
+
+    subgraph cli["cli"]
+    end
+
+    subgraph tui["TUI"]
+        commands_queue["Commands Queue"]
+        tui_state[("State")]
+
+        subgraph input["Input Processing (Daemon Thread)"]
+            commands_map["Commands Map"]
+        end
+
+        subgraph runner["Runner (Event Loop)"]
+        end
+
+        subgraph renderer["Renderer"]
+        end
+    end
+
+    subgraph exercise_iterator["Exercise Iterator"]
+    end
+
+    subgraph exercise_runner["Exercise Runner"]
+    end
+
+    subgraph watcher["File Watcher (Daemon Thread)"]
+    end
+
+    subgraph filesystem["Filesystem"]
+    end
+
+    %%connections%%
+    stdout --> user
+    user --> stdin --> input
+    stderr --> user
+
+    cli --> stdout
+    stdin --> cli
+    cli --> stderr
+    cli --starts--> runner
+
+    runner --> renderer --> stderr
+    runner --> renderer --> stdout
+    commands_map --push--> commands_queue
+
+    filesystem --polls--> watcher --refresh--> commands_queue
+
+    tui_state --> watcher
+    tui_state --> runner
+    tui_state <--> exercise_iterator
+    tui_state <--> exercise_runner
+```