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/MonthViewInteractionTests.swift

@@ -2,7 +2,7 @@
 //  MonthViewInteractionTests.swift
 //  Tests iOS
 //
-//  Month view interaction tests — tapping into month content.
+//  Month view interaction tests -- tapping and scrolling content.
 //
 
 import XCTest
@@ -10,79 +10,41 @@ import XCTest
 final class MonthViewInteractionTests: BaseUITestCase {
     override var seedFixture: String? { "week_of_moods" }
 
-    /// TC-030: Tap on month view content and verify interaction works without crash.
+    /// TC-030: Tap on month grid and verify the app remains stable.
     func testMonthView_TapContent_NoCrash() {
         let tabBar = TabBarScreen(app: app)
-
-        // 1. Navigate to Month tab
         tabBar.tapMonth()
-        XCTAssertTrue(tabBar.monthTab.isSelected, "Month tab should be selected")
 
-        // 2. Wait for month grid content to load
         let monthGrid = app.element(UITestID.Month.grid)
-        let scrollView = app.scrollViews.firstMatch
-
-        // Either the month_grid identifier or a scroll view should be present
-        let contentLoaded = monthGrid.waitForExistence(timeout: 5) ||
-                            scrollView.waitForExistence(timeout: 5)
-        XCTAssertTrue(contentLoaded, "Month view should have loaded content")
-
-        captureScreenshot(name: "month_view_before_tap")
-
-        // 3. Tap on the month view content (first cell/card in the grid)
-        //    Try the month_grid element first; fall back to tapping the scroll view content
-        if monthGrid.exists && monthGrid.isHittable {
-            monthGrid.tap()
-        } else if scrollView.exists && scrollView.isHittable {
-            // Tap near the center of the scroll view to hit a month card
-            scrollView.tap()
-        }
-
-        // 4. Verify the app did not crash — the tab bar should still be accessible
-        XCTAssertTrue(
-            tabBar.monthTab.waitForExistence(timeout: 5),
-            "App should remain stable after tapping month content"
+        monthGrid.waitUntilHittableOrFail(
+            timeout: navigationTimeout,
+            message: "Month grid should be hittable"
         )
 
-        // 5. Check if any detail/navigation occurred (look for navigation bar or content change)
-        //    Month view may show a detail view or popover depending on the card tapped
-        let navBar = app.navigationBars.firstMatch
-        let detailAppeared = navBar.waitForExistence(timeout: 3)
+        monthGrid.forceTap()
 
-        if detailAppeared {
-            captureScreenshot(name: "month_detail_view")
-        } else {
-            // No navigation occurred, which is also valid — the main check is no crash
-            captureScreenshot(name: "month_view_after_tap")
-        }
+        // Verify the tab bar is still present (app did not crash)
+        tabBar.assertVisible()
+
+        captureScreenshot(name: "month_view_after_tap")
     }
 
-    /// Navigate to Month tab with data, scroll down, and verify no crash.
+    /// Navigate to Month tab with data, scroll down/up, and verify no crash.
     func testMonthView_Scroll_NoCrash() {
         let tabBar = TabBarScreen(app: app)
-
-        // Navigate to Month tab
         tabBar.tapMonth()
-        XCTAssertTrue(tabBar.monthTab.isSelected, "Month tab should be selected")
 
-        // Wait for content to load
-        let scrollView = app.scrollViews.firstMatch
-        guard scrollView.waitForExistence(timeout: 5) else {
-            // If no scroll view, the month view may use a different layout — verify no crash
-            XCTAssertTrue(tabBar.monthTab.exists, "App should not crash on month view")
-            return
-        }
-
-        // Scroll down and up
-        scrollView.swipeUp()
-        scrollView.swipeDown()
-
-        // Verify the app is still stable
-        XCTAssertTrue(
-            tabBar.monthTab.waitForExistence(timeout: 3),
-            "App should remain stable after scrolling month view"
+        let monthGrid = app.element(UITestID.Month.grid)
+        monthGrid.waitForExistenceOrFail(
+            timeout: navigationTimeout,
+            message: "Month grid should be visible for scrolling"
         )
 
+        app.swipeUp()
+        app.swipeDown()
+
+        tabBar.assertVisible()
+
         captureScreenshot(name: "month_view_after_scroll")
     }
 }