fix(runner,sample-app): surface silent errors and demo a failing property (#15)

* fix(runner): surface non-deadline WaitForIdle errors

Previously the WaitForIdle return value was discarded entirely, hiding
real driver failures (gRPC transport errors, sidecar crashes) behind
the expected deadline-exceeded case. Log non-deadline errors so they
are visible without changing control flow.

* chore(sample-app): drop unused uptime_millis extractor

Registered in SampleApplication but never consumed by spec.ts.

* fix(sample-app): drop trivial appIsRunning property

app_state was hardcoded to 'running' so the property was a tautology
that could never fail. Removing both the extractor and the property
is the simplest fix; demo-grade properties that can fail land next.

* feat(sample-app): add Reset button that zeroes clickCount

Pairs with the next commit's tap-reset action so the fuzzer can
violate clickCountNeverDecreases and demonstrate uatu actually
finding a property violation.

* feat(sample-app): add tap-reset action to exercise Reset button

Weighted at 10/122, fuzzer reaches it within a short run. Pairs with
the Reset button to demonstrate uatu detecting the
clickCountNeverDecreases violation.

* fix(runner): filter WaitForIdle errors via context state, not errors.Is

errors.Is(err, context.DeadlineExceeded) misses gRPC's wrapped
status.DeadlineExceeded, so every step under the maestro driver
logged a spurious warning. Check idleCtx.Err() instead — captures
both deadline-fired and parent-canceled cases regardless of how the
driver wraps them.

* chore(sample-app): tune action weights so demo violates in ~30s

Prior weights left tap-reset rare enough that short demo runs missed
the violation by chance. Bumped to 30/107, with typeUsername reduced
since username noise doesn't help exercise clickCount.

* refactor(runner): route warnings through slog

Adds Options.Logger (defaults to slog.Default()) and converts the
three warning sites that were using fmt.Printf. Progress line stays
on Printf since it's user-facing UI, not a log. Makes the warnings
testable via a capturing handler.

* test(runner): assert WaitForIdle driver errors are logged

Captures slog output via TextHandler into a buffer and asserts the
warning message + injected error text appear when the mock driver
returns a non-context error from WaitForIdle. Guards against a
regression of the silent-error swallow.

examples/sample-app/android/src/main/kotlin/dev/uatu/sample/MainActivity.kt

@@ -47,6 +47,16 @@ class MainActivity : Activity() {
         }
         layout.addView(button)
 
+        val resetButton = Button(this).apply {
+            text = "Reset"
+            textSize = 18f
+            setOnClickListener {
+                clickCount = 0
+                label.text = "Clicks: $clickCount"
+            }
+        }
+        layout.addView(resetButton)
+
         val usernameLabel = TextView(this).apply {
             text = "Username: "
             textSize = 20f

examples/sample-app/android/src/main/kotlin/dev/uatu/sample/SampleApplication.kt

@@ -7,11 +7,7 @@ class SampleApplication : Application() {
     override fun onCreate() {
         super.onCreate()
         Uatu.start(this)
-        Uatu.extract("app_state") { "running" }
         Uatu.extract("click_count") { MainActivity.clickCount }
         Uatu.extract("username") { MainActivity.username }
-        Uatu.extract("uptime_millis") { System.currentTimeMillis() - startedAt }
     }
-
-    private val startedAt: Long = System.currentTimeMillis()
 }

examples/sample-app/spec.ts

@@ -11,9 +11,6 @@ import {
 
 // ── Snapshot extractors (fed by SampleApplication.kt) ──────────
 // See ./android/src/main/kotlin/dev/uatu/sample/SampleApplication.kt
-const appState = extract<string>(
-  (state) => (state.snapshots.app_state as string) ?? "",
-);
 const clickCount = extract<number>(
   (state) => (state.snapshots.click_count as number) ?? 0,
 );
@@ -23,11 +20,11 @@ const username = extract<string>(
 
 // ── UI elements ────────────────────────────────────────────────
 const clickButton = extract((state) => state.ax.find("text:Click me"));
+const resetButton = extract((state) => state.ax.find("text:Reset"));
 const usernameField = extract((state) => state.ax.find("desc:username_field"));
 
 // ── Properties ─────────────────────────────────────────────────
 export const properties = {
-  appIsRunning: always(() => appState.current === "running"),
   clickCountNonNegative: always(() => clickCount.current >= 0),
   clickCountNeverDecreases: always(() => {
     const previous = clickCount.previous;
@@ -50,10 +47,15 @@ const typeUsername = actions(() => {
     : [];
 });
 
+const tapReset = actions(() => {
+  return resetButton.current ? [Tap({ on: resetButton.current })] : [];
+});
+
 export const actionsRoot = weighted(
   [50, tapClickMe],
-  [50, typeUsername],
-  [10, taps],
+  [20, typeUsername],
+  [30, tapReset],
+  [5, taps],
   [2, swipes],
 );