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/YearViewDisplayTests.swift

@@ -12,27 +12,22 @@ final class YearViewDisplayTests: BaseUITestCase {
     override var seedFixture: String? { "week_of_moods" }
     override var bypassSubscription: Bool { true }
 
-    /// TC-035: Year View shows donut chart with mood distribution.
-    /// The donut chart center displays the entry count with "days" text.
+    /// TC-035: Year View shows the stats section containing the donut chart.
     func testYearView_DonutChartVisible() {
         let tabBar = TabBarScreen(app: app)
         tabBar.tapYear()
 
-        XCTAssertTrue(tabBar.yearTab.isSelected, "Year tab should be selected")
-
-        // Wait for stats section to render
         let statsSection = app.element(UITestID.Year.statsSection)
-        XCTAssertTrue(
-            statsSection.waitForExistence(timeout: 8),
-            "Year stats section should be visible"
+        statsSection.waitForExistenceOrFail(
+            timeout: navigationTimeout,
+            message: "Year stats section should be visible"
         )
 
-        // The donut chart center shows "days" — search globally since
-        // SwiftUI flattens the accessibility tree under GeometryReader.
+        // The donut chart center shows "days"
         let daysLabel = app.staticTexts["days"]
-        XCTAssertTrue(
-            daysLabel.waitForExistence(timeout: 3),
-            "Donut chart should display 'days' label in center"
+        daysLabel.waitForExistenceOrFail(
+            timeout: defaultTimeout,
+            message: "Donut chart should display 'days' label in center"
         )
 
         captureScreenshot(name: "year_donut_chart")
@@ -43,25 +38,22 @@ final class YearViewDisplayTests: BaseUITestCase {
         let tabBar = TabBarScreen(app: app)
         tabBar.tapYear()
 
-        XCTAssertTrue(tabBar.yearTab.isSelected, "Year tab should be selected")
-
         let statsSection = app.element(UITestID.Year.statsSection)
-        XCTAssertTrue(
-            statsSection.waitForExistence(timeout: 8),
-            "Year stats section should be visible"
+        statsSection.waitForExistenceOrFail(
+            timeout: navigationTimeout,
+            message: "Year stats section should be visible"
         )
 
         // week_of_moods fixture: 2 great, 2 good, 1 avg, 1 bad, 1 horrible
-        // Expected percentages: 28% (great, good) and 14% (avg, bad, horrible).
-        // Search for any of the expected percentage labels.
-        let found28 = app.staticTexts["28%"].waitForExistence(timeout: 3)
-        let found14 = app.staticTexts["14%"].waitForExistence(timeout: 2)
-
-        captureScreenshot(name: "year_bar_chart")
+        // Expected percentages: 28% or 14%
+        let found28 = app.staticTexts["28%"].waitForExistence(timeout: defaultTimeout)
+        let found14 = app.staticTexts["14%"].waitForExistence(timeout: defaultTimeout)
 
         XCTAssertTrue(
             found28 || found14,
             "Bar chart should show at least one percentage value (28% or 14%)"
         )
+
+        captureScreenshot(name: "year_bar_chart")
     }
 }