Rewrite all UI tests following fail-fast TEST_RULES patterns

Rewrote 60+ test files to follow honeydue-style test guidelines:
- defaultTimeout=2s, navigationTimeout=5s — fail fast, no long waits
- No coordinate taps (except onboarding paged TabView swipes)
- No sleep(), no retry loops
- No guard...else { return } silent passes — XCTFail everywhere
- All elements by accessibility ID via UITestID constants
- Screen objects for all navigation/actions/assertions
- One logical assertion per test method

Added missing accessibility identifiers to app views:
- MonthView.swift: added AccessibilityID.MonthView.grid to ScrollView
- YearView.swift: added AccessibilityID.YearView.heatmap to ScrollView

Framework rewrites:
- BaseUITestCase: added session ID, localeArguments, extraLaunchArguments
- WaitHelpers: waitForExistenceOrFail, waitUntilHittableOrFail,
  waitForNonExistence, scrollIntoView, forceTap
- All 7 screen objects rewritten with fail-fast semantics
- TEST_RULES.md added with non-negotiable rules

Known remaining issues:
- OnboardingTests: paged TabView swipes unreliable on iOS 26 simulator
- SettingsLegalLinksTests: EULA/Privacy buttons too deep in DEBUG scroll
- Customization horizontal picker scrolling needs further tuning

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Tests iOS/HierarchyDumpTest.swift

@@ -1,17 +1,23 @@
+//
+//  HierarchyDumpTest.swift
+//  Tests iOS
+//
+//  Debug helper: dumps the accessibility hierarchy for inspection.
+//
+
 import XCTest
 
-class HierarchyDumpTest: BaseUITestCase {
-    override var seedFixture: String? { nil }
+final class HierarchyDumpTest: BaseUITestCase {
 
+    /// Dump the accessibility tree for debug inspection.
     func testDumpAccessibilityTree() {
-        sleep(3)
+        // Wait for the app to settle
+        let tabBar = TabBarScreen(app: app)
+        tabBar.assertVisible()
 
         print("\n=== ELEMENT QUERIES ===")
-        print("otherElements[mood_header]: \(app.otherElements["mood_header"].exists)")
-        print("descendants[mood_header]: \(app.descendants(matching: .any)["mood_header"].firstMatch.exists)")
-        print("groups[mood_header]: \(app.groups["mood_header"].exists)")
-        print("scrollViews[mood_header]: \(app.scrollViews["mood_header"].exists)")
-        print("staticTexts[mood_header]: \(app.staticTexts["mood_header"].exists)")
+        print("otherElements[mood_header]: \(app.otherElements[UITestID.Day.moodHeader].exists)")
+        print("descendants[mood_header]: \(app.element(UITestID.Day.moodHeader).exists)")
         print("buttons[mood_button_great]: \(app.buttons["mood_button_great"].exists)")
         print("tabBars count: \(app.tabBars.count)")
         if app.tabBars.count > 0 {
@@ -20,7 +26,6 @@ class HierarchyDumpTest: BaseUITestCase {
                 print("  tab button: \(b.identifier) label=\(b.label)")
             }
         }
-        print("otherElements[settings_header]: \(app.otherElements["settings_header"].exists)")
 
         print("\n=== HIERARCHY (first 200 lines) ===")
         let desc = app.debugDescription
@@ -29,6 +34,7 @@ class HierarchyDumpTest: BaseUITestCase {
             print("\(i): \(line)")
         }
 
-        XCTAssertTrue(true) // always pass
+        // Always pass -- this is a debug/diagnostic test
+        XCTAssertTrue(true)
     }
 }