feat(api): streamline generated app authoring

Move the canonical examples toward generated component-root helpers, typed form decoding, async/state handler registration, and derive-driven app/component registry wiring. Tighten requirements and diagnostics for the server-first, selectorless authoring path.

Verified with cargo run -p slhx-xtask -- test, cargo check --workspace, redgate list, redgate refs, redgate health --strict, and git diff --check.

req: canonical/001

req: canonical/003

req: canonical/004

req: dx/002

req: derive_app/001

req: component/003

req: form/004

req: axum_integration/003

slhx-test/tests/inspector.rs

@@ -1,14 +1,13 @@
-use slhx_core::{Atom, Effect, KeyedSlot, Payload, ResourceRef, Slot};
+use slhx_core::{
+    Atom, Effect, GeneratedTarget, KeyedSlot, Payload, ResourceId, ResourceKind, ResourceRef, Slot,
+};
 
 #[test]
 fn inspects_tuple_effects() {
     let count = Slot::<u32>::new(1);
     let user = Atom::<String>::new(2);
 
-    let inspected = slhx_test::run(
-        |value| (count.text(value), user.set("alice")),
-        42,
-    );
+    let inspected = slhx_test::run(|value| (count.text(value), user.set("alice")), 42);
 
     assert!(inspected.has_slot(count));
     assert!(inspected.has_atom(user));
@@ -26,3 +25,116 @@ fn finds_keyed_slot_targets() {
     assert!(inspected.has_keyed_slot(rows));
     assert_eq!(inspected.ops().len(), 1);
 }
+
+#[test]
+fn builds_generated_handle_form_bodies() {
+    let handle = slhx_core::Handle::<()>::new(7);
+
+    let body = slhx_test::handle_form_body(handle, &[("title", "hello world"), ("tag", "a&b")]);
+
+    assert_eq!(body, "__h=7&title=hello+world&tag=a%26b");
+    assert_eq!(slhx_test::unknown_handle_form_body(99), "__h=99");
+}
+
+#[test]
+fn builds_authoring_boundary_selectors() {
+    assert_eq!(
+        slhx_test::root_selector("techdemo"),
+        r#"[data-slhx-root="techdemo"]"#
+    );
+    assert_eq!(
+        slhx_test::island_selector("orbit"),
+        r#"[data-slhx-island="orbit"]"#
+    );
+    assert_eq!(slhx_test::island_attribute_name(), "data-slhx-island");
+    assert_eq!(slhx_test::island_event_name("orbit"), "slhx:island-orbit");
+    assert_eq!(
+        slhx_test::sse_endpoint_marker("/events"),
+        r#"data-slhx-sse="/events""#
+    );
+    assert_eq!(slhx_test::any_root_selector(), "[data-slhx-root]");
+    assert_eq!(
+        slhx_test::root_element_selector("main", "docs"),
+        r#"main[data-slhx-root="docs"]"#
+    );
+    assert_eq!(slhx_test::document_body_selector(), "body");
+    assert_eq!(slhx_test::document_title_selector(), "title");
+    assert_eq!(
+        slhx_test::runtime_script_selector(),
+        r#"script[src="/slhx.js"]"#
+    );
+    assert_eq!(
+        slhx_test::target_selector(TestTarget(ResourceKind::Slot, 42)),
+        r#"[data-sid="42"]"#
+    );
+    assert_eq!(
+        slhx_test::handle_button_selector(slhx_core::Handle::<()>::new(7)),
+        r#"button[data-hid="7"]"#
+    );
+    assert_eq!(slhx_test::article_selector(), "article");
+    assert_eq!(slhx_test::strong_text_selector(), "strong");
+    assert_eq!(slhx_test::small_text_selector(), "small");
+    assert_eq!(slhx_test::escaped_markup_selector("b"), "b");
+    assert_eq!(slhx_test::heading_selector("article", 1), "article h1");
+    assert_eq!(slhx_test::list_item_selector("ul"), "ul li");
+    assert_eq!(slhx_test::prose_selector("article"), "article p");
+    assert_eq!(slhx_test::form_selector("header"), "header form");
+    assert_eq!(
+        slhx_test::select_options_selector("column"),
+        r#"select[name="column"] > option"#
+    );
+    assert_eq!(slhx_test::class_selector("lane"), ".lane");
+    assert_eq!(
+        slhx_test::element_class_selector("span", "presence"),
+        "span.presence"
+    );
+    assert_eq!(
+        slhx_test::class_child_selector("columns", "section", "column"),
+        ".columns > section.column"
+    );
+    assert_eq!(
+        slhx_test::class_descendant_selector("impact", "i"),
+        ".impact i"
+    );
+    assert_eq!(slhx_test::disabled_button_selector(), "button[disabled]");
+    assert_eq!(
+        slhx_test::nav_link_selector("/architecture"),
+        r#"a[href="/architecture"]"#
+    );
+    assert_eq!(
+        slhx_test::page_nav_link_selector("/docs"),
+        r#"a[href="/docs"][data-slhx-nav]:not([data-slhx-handle])"#
+    );
+    assert_eq!(slhx_test::island_snapshot_marker(), "data-island-snapshot=");
+    assert_eq!(
+        slhx_test::island_readout_selector(),
+        "[data-island-readout]"
+    );
+    assert_eq!(
+        slhx_test::scoped_island_readout_selector("#probe-island"),
+        "#probe-island [data-island-readout]"
+    );
+    assert_eq!(
+        slhx_test::keyed_selector(".work-card", 4),
+        r#".work-card[data-key="4"]"#
+    );
+    assert_eq!(slhx_test::keyed_items_selector("li"), "li[data-key]");
+
+    let probe = slhx_test::island_probe_script(
+        "probe-island",
+        "orbit",
+        "1|1|1|probe waiting",
+        "7|2|8|probe live",
+    );
+    assert!(probe.contains("probe-island"));
+    assert!(probe.contains("probe live"));
+}
+
+#[derive(Clone, Copy)]
+struct TestTarget(ResourceKind, u32);
+
+impl GeneratedTarget for TestTarget {
+    fn __slhx_resource_id(self) -> ResourceId {
+        ResourceId::new(self.0, self.1)
+    }
+}