fix(sample-app): address PR #18 review findings (#19)

- WebLedgerStore.accountExistsByName case-insensitive (matches SQL COLLATE NOCASE)
- drop SampleApplication.maybeInjectDebugError; sample spec now passes clean
- drop noLogcatErrors from sample spec (default matches system-wide E logs)
- openRandomAccount picks uniformly from findAll instead of first match
- clear txnError on any add-transaction interaction, not only valid amount input
- escapeForAdbInputText quotes shell metacharacters (quotes, backslash, etc.)
- extract buildClearKeyevents helper with empty/normal/cap tests
- broaden spec_integration_test.go to cover home, add-account, ledger,
  add-transaction action generators
- document FocusTracker single-focus invariant

sidecar/src/main/kotlin/dev/uatu/sidecar/DriverBackend.kt

@@ -93,6 +93,32 @@ class StubDriverBackend(private val platform: String) : DriverBackend {
         // hierarchy that reports an enormous text length for the focused field.
         internal const val MAX_CLEAR_DELETES: Int = 1024
 
+        internal fun buildClearKeyevents(textLength: Int): List<String> {
+            if (textLength <= 0) return emptyList()
+            val deletes = minOf(textLength, MAX_CLEAR_DELETES)
+            val args = mutableListOf("shell", "input", "keyevent", "KEYCODE_MOVE_END")
+            repeat(deletes) { args.add("KEYCODE_DEL") }
+            return args
+        }
+
+        // `adb shell input text` runs through a remote sh, so shell metacharacters
+        // in the payload would be interpreted by the device shell. Substitute
+        // spaces with %s (input's escape) and backslash-escape characters sh
+        // would otherwise expand. Keep this list conservative; anything not
+        // listed passes through literally.
+        internal fun escapeForAdbInputText(text: String): String {
+            val sb = StringBuilder(text.length)
+            for (ch in text) {
+                when (ch) {
+                    ' ' -> sb.append("%s")
+                    '\\', '"', '\'', '&', '|', ';', '<', '>', '(', ')', '*', '?',
+                    '$', '`', '[', ']', '{', '}', '~', '#', -> sb.append('\\').append(ch)
+                    else -> sb.append(ch)
+                }
+            }
+            return sb.toString()
+        }
+
         // Matches a uiautomator-dump <node ...> tag where `focused="true"` is
         // present. Captures only the tag's attribute string so we can pull
         // `text="..."` out of it without building a full XML tree.
@@ -188,16 +214,13 @@ class StubDriverBackend(private val platform: String) : DriverBackend {
         // pure replace: read the current value's length from the hierarchy,
         // then move-end + N backspaces before typing.
         clearFocusedField()
-        runAdb(listOf("shell", "input", "text", text.replace(" ", "%s")))
+        runAdb(listOf("shell", "input", "text", escapeForAdbInputText(text)))
     }
 
     private fun clearFocusedField() {
         val current = focusedFieldText() ?: return
         if (current.isEmpty()) return
-        val deletes = minOf(current.length, MAX_CLEAR_DELETES)
-        val keyevents = mutableListOf("shell", "input", "keyevent", "KEYCODE_MOVE_END")
-        repeat(deletes) { keyevents.add("KEYCODE_DEL") }
-        runAdb(keyevents)
+        runAdb(buildClearKeyevents(current.length))
     }
 
     private fun focusedFieldText(): String? {

sidecar/src/test/kotlin/dev/uatu/sidecar/InputTextClearTest.kt

@@ -3,9 +3,51 @@ package dev.uatu.sidecar
 import org.junit.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertNull
+import kotlin.test.assertTrue
 
 class InputTextClearTest {
 
+    @Test fun buildClearKeyeventsEmptyWhenNothingToDelete() {
+        assertEquals(emptyList(), StubDriverBackend.buildClearKeyevents(0))
+        assertEquals(emptyList(), StubDriverBackend.buildClearKeyevents(-3))
+    }
+
+    @Test fun buildClearKeyeventsPrefixesMoveEndThenOneDelPerChar() {
+        val args = StubDriverBackend.buildClearKeyevents(3)
+        assertEquals(listOf("shell", "input", "keyevent", "KEYCODE_MOVE_END",
+            "KEYCODE_DEL", "KEYCODE_DEL", "KEYCODE_DEL"), args)
+    }
+
+    @Test fun buildClearKeyeventsCapsAtMaxClearDeletes() {
+        val huge = StubDriverBackend.MAX_CLEAR_DELETES * 10
+        val args = StubDriverBackend.buildClearKeyevents(huge)
+        val deletes = args.count { it == "KEYCODE_DEL" }
+        assertEquals(StubDriverBackend.MAX_CLEAR_DELETES, deletes)
+        assertEquals("KEYCODE_MOVE_END", args[3])
+    }
+
+    @Test fun escapeForAdbInputTextSubstitutesSpaces() {
+        assertEquals("hello%sworld", StubDriverBackend.escapeForAdbInputText("hello world"))
+    }
+
+    @Test fun escapeForAdbInputTextEscapesShellMetacharacters() {
+        val escaped = StubDriverBackend.escapeForAdbInputText("a&b|c;d\$e`f")
+        assertEquals("a\\&b\\|c\\;d\\\$e\\`f", escaped)
+    }
+
+    @Test fun escapeForAdbInputTextEscapesQuotesAndBackslash() {
+        assertEquals("\\'", StubDriverBackend.escapeForAdbInputText("'"))
+        assertEquals("\\\"", StubDriverBackend.escapeForAdbInputText("\""))
+        assertEquals("\\\\", StubDriverBackend.escapeForAdbInputText("\\"))
+    }
+
+    @Test fun escapeForAdbInputTextLeavesSimpleTextAlone() {
+        assertEquals("12.34", StubDriverBackend.escapeForAdbInputText("12.34"))
+        assertEquals("Coffee", StubDriverBackend.escapeForAdbInputText("Coffee"))
+        assertTrue("-5" == StubDriverBackend.escapeForAdbInputText("-5"))
+    }
+
+
     @Test fun parsesTextFromFocusedNode() {
         val xml = """
             <hierarchy>