Refactor: untangle framework library from todo example

The codebase is now split into two clear layers:

Framework library (src/):
- lib.rs — public API surface, re-exports all framework types
- signal.rs — SignalOpts, Signal, SignalStore, mangle/global/client_only helpers
- query.rs — Query trait, CacheKey, query_one!/query_all! macros
  (macro paths updated from $crate::framework::* to $crate::*)
- context.rs — RenderContext, ComponentTree, ComponentNode
- connection.rs — ConnectionManager, SubscriptionRegistry, ConnectionState
- sse.rs — format_patch_elements, format_patch_signals
- server.rs — AppState, SharedState, sse_handler (pure framework plumbing)

Todo example (examples/todo/):
- main.rs — SQLite setup, seeding, server bootstrap
- app.rs — router, document_shell, resolve_and_render, render_page,
  action_then_render, and all HTTP handlers
- queries.rs — Todo model, ListTodos/GetTodo queries, mutation helpers
- todo_list.rs — TodoList page component
- about.rs — About page component

Run the example independently with: cargo run --example todo

https://claude.ai/code/session_01JThiQbp3Bn9J1VhBpRuz4u

examples/todo/todo_list.rs

@@ -0,0 +1,121 @@
+use crate::queries::{ListTodos, Todo};
+use livevue_rs::{RenderContext, global, mangle};
+use maud::{html, Markup};
+
+/// Root page component: renders the full todo list with add form.
+///
+/// Reads signals:
+/// - `newTodo` (global, server-relevant): the text input value
+///
+/// Exercises:
+/// - `cx.run()` for data fetching
+/// - `cx.signal()` with `global()` scoping + `Signal::val` in expressions
+/// - `cx.signal()` with `mangle().client_only()` scoping (in todo_item)
+/// - DataStar `data-bind`, `data-on-click`, `data-attr` attributes
+/// - `@post()` actions for mutations
+pub async fn todo_list(cx: &mut RenderContext) -> anyhow::Result<Markup> {
+    // Fetch all todos
+    let todos = cx.run(ListTodos).await?;
+
+    // Global signal for the "new todo" input. This call does two things:
+    // 1. Records "newTodo" as a touched signal (for demangling tracking)
+    // 2. Returns a Signal struct whose .val is "$newTodo" for expressions
+    let new_todo = cx.signal("newTodo", global());
+
+    let todo_count = todos.len();
+    let done_count = todos.iter().filter(|t| t.completed).count();
+
+    Ok(html! {
+        div.todo-app {
+            h1 { "LiveVue.rs — Todo List" }
+
+            // Navigation link to About page (exercises tree signal + page routing)
+            nav {
+                span.nav-current { "Todos" }
+                " | "
+                button.nav-link
+                    data-on-click="$tree = {page: 'About'}; @post('/render')" {
+                    "About"
+                }
+            }
+
+            // Add todo form.
+            // data-bind-newTodo binds the input to the $newTodo signal.
+            // The button uses new_todo.val ("$newTodo") in a DataStar expression.
+            div.add-form {
+                input
+                    type="text"
+                    placeholder="What needs to be done?"
+                    data-bind-newTodo=""
+                    ;
+                button
+                    data-on-click="@post('/action/add_todo')"
+                    data-attr=(format!("{{disabled: {}.trim() === ''}}", new_todo.val)) {
+                    "Add"
+                }
+            }
+
+            // Stats
+            p.stats {
+                (format!("{} items, {} completed", todo_count, done_count))
+            }
+
+            // Todo items
+            ul.todo-list {
+                @for todo in &todos {
+                    (todo_item(cx, todo))
+                }
+            }
+
+            @if todos.is_empty() {
+                p.empty { "No todos yet. Add one above!" }
+            }
+        }
+    })
+}
+
+/// Renders a single todo item.
+///
+/// This is a static child component — called directly from `todo_list`,
+/// not resolved through the component registry.
+///
+/// Demonstrates per-instance, client-only signal via `mangle().client_only()`.
+fn todo_item(cx: &mut RenderContext, todo: &Todo) -> Markup {
+    // Per-instance, client-only signal for edit mode.
+    // Not used in v0 rendering, but demonstrates the mangled signal API
+    // and ensures it's tracked as touched. Produces: "_editing__<id>"
+    let _editing = cx.signal("editing", mangle(todo.id).client_only());
+
+    // Build class string server-side. Since we do a full rerender on every
+    // state change, there's no need for data-class here — the server knows
+    // whether the todo is completed.
+    let title_class = if todo.completed {
+        "todo-title completed"
+    } else {
+        "todo-title"
+    };
+
+    html! {
+        li.todo-item id=(format!("todo-{}", todo.id)) {
+            // Checkbox to toggle completion.
+            // `checked[expr]` is maud's syntax for conditional boolean attributes.
+            input
+                type="checkbox"
+                checked[todo.completed]
+                data-on-click=(format!("@post('/action/toggle_todo?id={}')", todo.id))
+                ;
+
+            // Title with strikethrough when completed (class set server-side)
+            span class=(title_class) {
+                (todo.title)
+            }
+
+            // Delete button
+            button.delete-btn
+                data-on-click=(format!("@post('/action/delete_todo?id={}')", todo.id))
+                {
+                "×"
+            }
+        }
+    }
+}