refactor: Replace ad-hoc dispatch with FSM + driver architecture (#3434)

Replaces the tangled dispatch handler system (`tui/dispatch.rs`,
`tui/state.rs`) with a pure finite state machine + driver architecture.
The FSM handles all state transitions as explicit `(State, Event) →
(NewState, Effects)` mappings. The driver executes IO effects and
bridges the TUI to the FSM.

3 files changed, 14 insertions, 12 deletions

diff --git a/crates/atuin-ai/src/tui/components/atuin_ai.rs b/crates/atuin-ai/src/tui/components/atuin_ai.rs
index c7227fbd..31dff1c3 100644
--- a/crates/atuin-ai/src/tui/components/atuin_ai.rs
+++ b/crates/atuin-ai/src/tui/components/atuin_ai.rs
@@ -5,11 +5,10 @@
 //! Tab) are handled in the bubble phase so child components like the
 //! permission Select can consume them first.
 
-use std::sync::mpsc;
-
 use crossterm::event::{Event, KeyCode, KeyEvent, KeyEventKind, KeyModifiers};
 use eye_declare::{Elements, EventResult, Hooks, component, props};
 
+use crate::commands::inline::DriverEventSender;
 use crate::tui::events::AiTuiEvent;
 use crate::tui::state::AppMode;
 
@@ -28,7 +27,7 @@ pub(crate) struct AtuinAi {
 
 #[derive(Default)]
 pub(crate) struct AtuinAiState {
-    tx: Option<mpsc::Sender<AiTuiEvent>>,
+    tx: Option<DriverEventSender>,
 }
 
 #[component(props = AtuinAi, state = AtuinAiState, children = Elements)]
@@ -38,7 +37,7 @@ fn atuin_ai(
     hooks: &mut Hooks<AtuinAi, AtuinAiState>,
     children: Elements,
 ) -> Elements {
-    hooks.use_context::<mpsc::Sender<AiTuiEvent>>(|tx, _, state| {
+    hooks.use_context::<DriverEventSender>(|tx, _, state| {
         state.tx = tx.cloned();
     });
 
diff --git a/crates/atuin-ai/src/tui/components/input_box.rs b/crates/atuin-ai/src/tui/components/input_box.rs
index 6e041418..6b81322c 100644
--- a/crates/atuin-ai/src/tui/components/input_box.rs
+++ b/crates/atuin-ai/src/tui/components/input_box.rs
@@ -6,7 +6,7 @@
 //!
 //! On Enter, sends `AiTuiEvent::SubmitInput` via the context-provided channel.
 
-use std::sync::{Arc, Mutex, mpsc};
+use std::sync::{Arc, Mutex};
 
 use crossterm::event::KeyModifiers;
 use eye_declare::{Canvas, Elements, EventResult, Hooks, component, element, props};
@@ -19,6 +19,7 @@ use ratatui_core::{
 };
 use tui_textarea::TextArea;
 
+use crate::commands::inline::DriverEventSender;
 use crate::tui::{events::AiTuiEvent, slash::SlashCommandSearchResult};
 
 /// A bordered text input box backed by tui-textarea.
@@ -41,7 +42,7 @@ pub(crate) struct InputBox {
 
 pub(crate) struct InputBoxState {
     textarea: Arc<Mutex<TextArea<'static>>>,
-    tx: Option<mpsc::Sender<AiTuiEvent>>,
+    tx: Option<DriverEventSender>,
 }
 
 impl Default for InputBoxState {
@@ -97,10 +98,13 @@ fn input_box(
     state: &InputBoxState,
     hooks: &mut Hooks<InputBox, InputBoxState>,
 ) -> Elements {
-    hooks.use_focusable(props.active);
+    // Always focusable so focus isn't lost when the permission Select is
+    // removed from the tree. The `active` prop controls visual state and
+    // whether keystrokes are processed, not focusability.
+    hooks.use_focusable(true);
     hooks.use_autofocus();
 
-    hooks.use_context::<mpsc::Sender<AiTuiEvent>>(|tx, _, state| {
+    hooks.use_context::<DriverEventSender>(|tx, _, state| {
         state.tx = tx.cloned();
     });
 
diff --git a/crates/atuin-ai/src/tui/components/select.rs b/crates/atuin-ai/src/tui/components/select.rs
index 5abbe655..771d7830 100644
--- a/crates/atuin-ai/src/tui/components/select.rs
+++ b/crates/atuin-ai/src/tui/components/select.rs
@@ -1,10 +1,9 @@
-use std::sync::mpsc;
-
 use crossterm::event::KeyCode;
 use eye_declare::{Elements, EventResult, Hooks, Span, Text, View, component, element, props};
 use ratatui::style::Style;
 use typed_builder::TypedBuilder;
 
+use crate::commands::inline::DriverEventSender;
 use crate::tui::events::AiTuiEvent;
 
 type OnSelectFn = Box<dyn Fn(&SelectOption) -> Option<AiTuiEvent> + Send + Sync + 'static>;
@@ -24,7 +23,7 @@ pub(crate) struct SelectOption {
 #[derive(Default)]
 pub(crate) struct PermissionSelectorState {
     selected_option: usize,
-    tx: Option<mpsc::Sender<AiTuiEvent>>,
+    tx: Option<DriverEventSender>,
 }
 
 #[props]
@@ -42,7 +41,7 @@ pub(crate) fn permission_selector(
     hooks.use_focusable(true);
     hooks.use_autofocus();
 
-    hooks.use_context::<mpsc::Sender<AiTuiEvent>>(|tx, _, state| {
+    hooks.use_context::<DriverEventSender>(|tx, _, state| {
         state.tx = tx.cloned();
     });