fix(examples): use lower-aware slot html updates

Move canonical examples and docs off direct RenderSlotExt render shortcuts so slot updates use generated render/lowering before HTML replacement, preserving runtime metadata for follow-up interactions.

req: component/003

req: runtime/001

req: dx/006

req: examples/003

slhx-test/tests/examples_contract.rs

@@ -116,6 +116,7 @@ fn canonical_example_docs_do_not_teach_low_level_plumbing() {
         "lower_html(",
         "render_html(",
         "SafeHtml::trusted",
+        ".render(&",
     ];
     let mut failures = Vec::new();
     scan_examples(&examples, &mut |path, text| {