test(xtask): assert html examples avoid reloads

Wrap html_examples browser smoke interactions with a no-navigation guard so dynamic paths fail if native form fallback or full-page reload occurs.

req: test/014

req: test/006

AGENTS.md

@@ -51,7 +51,7 @@ Keep it stable. Prefer pointers to canonical sources over copied structure, file
 - Add only durable style, ownership, gotchas, and at most a few stable commands agents should actually run.
 - Prefer links or pointers to canonical sources over copied lists.
 - Avoid project trees, architecture maps, generated inventories, current file sizes, issue lists, TODO inventories, and other snapshots that will rot.
-- Stable commands: `cargo run -p hemx-xtask -- test`, `cargo run -p hemx-xtask -- html-examples-smoke`, `cargo check --workspace`, `redgate health --strict`. Use the xtask runner for full verification so jobs are capped from local CPU and memory; use the html_examples smoke for focused repo-owned browser verification of the HTML pattern gallery, not `/tmp` scripts. req: test/004 req: test/006 req: test/012 req: test/013
+- Stable commands: `cargo run -p hemx-xtask -- test`, `cargo run -p hemx-xtask -- html-examples-smoke`, `cargo check --workspace`, `redgate health --strict`. Use the xtask runner for full verification so jobs are capped from local CPU and memory; use the html_examples smoke for focused repo-owned browser verification of the HTML pattern gallery, no-reload dynamic interactions, and no `/tmp` scripts. req: test/004 req: test/006 req: test/012 req: test/013 req: test/014
 - Example behavior tests should prefer `hemx_test` generated-resource assertions over raw slot constants or raw effect/payload matching; keep browser selector helpers as test adapters only, not authoring APIs. req: test/008 req: test/009 req: test/010
 - Run the workout product exemplar with `cargo run -p hemx-xtask -- workout dev` and open `http://127.0.0.1:3028`; set `HEMX_WORKOUT_ADDR=127.0.0.1:3030` if the default port is busy. Its durable visual direction and recovery expectations live in `examples/workout/DESIGN.md`. req: examples/008
 - Use the same Workout command surface for tests, production build, and mobile release: `cargo run -p hemx-xtask -- workout test`, `cargo run -p hemx-xtask -- workout build`, `HEMX_WORKOUT_ORIGIN=https://workout.example.com cargo run -p hemx-xtask -- workout mobile-release`, and `HEMX_WORKOUT_ORIGIN=https://workout.example.com cargo run -p hemx-xtask -- workout mobile-verify`; Android/iOS SDKs, store submission targets, and signing remain external blockers, not repo-owned secrets, and do not imply a broad `hemx-mobile` framework. req: examples/006 req: examples/011 req: examples/013

REQUIREMENTS.md

@@ -856,6 +856,9 @@ what a valid business email is. [north_star]
 ### req: test/013
 0	013	Durable browser coverage must not rely on ad hoc `/tmp` scripts. [north_star]
 
+### req: test/014
+0	014	html_examples browser smoke asserts dynamic interactions complete without full-page reload or navigation. [north_star]
+
 ---
 
 ## check

hemx-xtask/src/main.rs

@@ -103,7 +103,10 @@ fn run_html_examples_smoke() -> ExitCode {
     if let Err(code) = cdp_wait_for_html_examples() {
         return code;
     }
-    if let Err(code) = cdp_assert("revealed fallback without IntersectionObserver", REVEALED_FALLBACK_SMOKE) {
+    if let Err(code) = cdp_assert(
+        "revealed fallback without IntersectionObserver",
+        REVEALED_FALLBACK_SMOKE,
+    ) {
         return code;
     }
     println!("html_examples smoke ok: revealed fallback without IntersectionObserver");
@@ -124,7 +127,10 @@ fn pick_unused_port() -> Result<u16, ExitCode> {
 fn start_html_examples_server(addr: &str) -> Result<HtmlExamplesServer, ExitCode> {
     let mut child = Command::new("cargo")
         .args(["run", "-p", "hemx-html-examples"])
-        .env("HEMX_HTML_EXAMPLES_PORT", addr.rsplit(':').next().unwrap_or("3029"))
+        .env(
+            "HEMX_HTML_EXAMPLES_PORT",
+            addr.rsplit(':').next().unwrap_or("3029"),
+        )
         .stdout(Stdio::null())
         .stderr(Stdio::null())
         .spawn()
@@ -206,7 +212,9 @@ fn cdp_wait_for_html_examples() -> Result<(), ExitCode> {
                 ExitCode::FAILURE
             })?;
         if output.status.success()
-            && String::from_utf8_lossy(&output.stdout).trim().ends_with("true")
+            && String::from_utf8_lossy(&output.stdout)
+                .trim()
+                .ends_with("true")
         {
             return Ok(());
         }
@@ -217,8 +225,23 @@ fn cdp_wait_for_html_examples() -> Result<(), ExitCode> {
 }
 
 fn cdp_assert(name: &str, script: &str) -> Result<(), ExitCode> {
+    // Each interaction must be handled by hemx without full-page navigation or
+    // reload; failures here catch native form fallback sneaking into the smoke. req: test/014
+    let guarded_script = format!(
+        r#"(async()=>{{
+            const __hemxSmokeUrl = location.href;
+            const __hemxSmokeMarker = String(Date.now()) + Math.random();
+            const __hemxSmokeNavCount = performance.getEntriesByType("navigation").length;
+            window.__hemxSmokeNoReload = __hemxSmokeMarker;
+            const __hemxSmokeResult = await ({script});
+            if (location.href !== __hemxSmokeUrl) throw new Error("page navigated during smoke interaction");
+            if (window.__hemxSmokeNoReload !== __hemxSmokeMarker) throw new Error("page reloaded during smoke interaction");
+            if (performance.getEntriesByType("navigation").length !== __hemxSmokeNavCount) throw new Error("navigation entry changed during smoke interaction");
+            return __hemxSmokeResult;
+        }})()"#
+    );
     let output = Command::new("cdp-browser")
-        .args(["js", script])
+        .args(["js", &guarded_script])
         .output()
         .map_err(|err| {
             eprintln!("failed to run browser smoke `{name}`: {err}");