test(xtask): cover revealed fallback smoke

Add a deterministic html_examples browser smoke path that reloads the runtime with IntersectionObserver disabled and verifies data-hemx-revealed fallback dispatch.

req: convention/014

req: test/006

hemx-xtask/src/main.rs

@@ -95,6 +95,19 @@ fn run_html_examples_smoke() -> ExitCode {
         println!("html_examples smoke ok: {name}");
     }
 
+    // Re-load the runtime with IntersectionObserver disabled to exercise the
+    // deterministic revealed fallback path in a real browser. req: convention/014 req: test/006
+    if let Err(code) = cdp_tab_goto(&url) {
+        return code;
+    }
+    if let Err(code) = cdp_wait_for_html_examples() {
+        return code;
+    }
+    if let Err(code) = cdp_assert("revealed fallback without IntersectionObserver", REVEALED_FALLBACK_SMOKE) {
+        return code;
+    }
+    println!("html_examples smoke ok: revealed fallback without IntersectionObserver");
+
     ExitCode::SUCCESS
 }
 
@@ -229,6 +242,7 @@ const DELETE_ROW_SMOKE: &str = r#"(async()=>{const text=()=>document.body.textCo
 const LAZY_LOAD_SMOKE: &str = r#"(async()=>{const f=Array.from(document.querySelectorAll("form")).find(f=>f.textContent.includes("Load lazy content")); const panel=()=>f.nextElementSibling; const before=panel().textContent.trim(); f.querySelector("button,input[type=submit]").click(); await new Promise(r=>setTimeout(r,700)); const after=panel().textContent.trim(); if(!(after.includes("Lazy content loaded by server update #")&&after!==before)) throw new Error("lazy load did not visibly update"); return true;})()"#;
 const CLICK_TO_LOAD_SMOKE: &str = r#"(async()=>{const text=()=>document.body.textContent.replace(/\s+/g," "); const f=Array.from(document.querySelectorAll("form")).find(f=>f.textContent.includes("Load more")); f.querySelector("button,input[type=submit]").click(); await new Promise(r=>setTimeout(r,700)); if(!(text().includes("Loaded row 3")&&text().includes("Loaded row 4"))) throw new Error("click-to-load did not append rows"); return true;})()"#;
 const INFINITE_SCROLL_SMOKE: &str = r#"(async()=>{const text=()=>document.body.textContent.replace(/\s+/g," "); const f=Array.from(document.querySelectorAll("form")).find(f=>f.textContent.includes("Reveal more rows")); f.querySelector("button,input[type=submit]").click(); await new Promise(r=>setTimeout(r,700)); if(!(text().includes("Loaded row 4")&&text().includes("Loaded row 6"))) throw new Error("infinite scroll did not append rows"); return true;})()"#;
+const REVEALED_FALLBACK_SMOKE: &str = r#"(async()=>{const text=()=>document.body.textContent.replace(/\s+/g," "); const runtime=document.querySelector('script[src*="hemx"][src$=".js"]'); if(!runtime) throw new Error("runtime script not found"); Object.defineProperty(window,"IntersectionObserver",{value:undefined,configurable:true}); const reloaded=document.createElement("script"); reloaded.src=runtime.src; document.head.appendChild(reloaded); for(let i=0;i<20;i++){if(text().includes("Lazy content loaded by server update #")&&text().includes("Loaded row 4")&&text().includes("Loaded row 6")) return true; await new Promise(r=>setTimeout(r,150));} throw new Error("revealed fallback did not dispatch lazy/infinite forms without a click");})()"#;
 const PROGRESS_SMOKE: &str = r#"(async()=>{const f=Array.from(document.querySelectorAll("form")).find(f=>f.textContent.includes("Tick progress")); const text=()=>document.querySelector("progress").textContent.trim(); const before=text(); f.querySelector("button,input[type=submit]").click(); await new Promise(r=>setTimeout(r,700)); const after=text(); if(!(after!==before&&after!=="100% complete"&&after.endsWith("% complete"))) throw new Error("progress click did not visibly tick"); return true;})()"#;
 const VALUE_SELECT_SMOKE: &str = r#"(async()=>{const f=Array.from(document.querySelectorAll("form")).find(f=>f.elements.category); f.elements.category.value="numbers"; f.elements.category.dispatchEvent(new Event("change",{bubbles:true,cancelable:true})); f.querySelector("button,input[type=submit]").click(); await new Promise(r=>setTimeout(r,700)); const options=Array.from(document.querySelectorAll("select[name=value] option")).map(option=>option.textContent.trim()); if(!(options.includes("One")&&options.includes("Two")&&!options.includes("Alpha"))) throw new Error("value select did not replace options"); return true;})()"#;
 const RESET_INPUT_SMOKE: &str = r#"(async()=>{const f=Array.from(document.querySelectorAll("form")).find(f=>f.elements.message); f.elements.message.value="hello reset"; f.querySelector("button,input[type=submit]").click(); await new Promise(r=>setTimeout(r,700)); if(!(document.body.textContent.includes("Sent: hello reset")&&f.elements.message.value==="")) throw new Error("reset user input did not clear field"); return true;})()"#;