refactor: move rule editor actions into the navigation bar

- Both editor modes commit via a checkmark confirmation button
  (role: .confirm) in the navigation bar — accessibility labels
  'Add Rule' (create) and 'Done' (edit); replaces the bottom
  'Add Rule' button, so nothing floats over the form anymore
- Edit mode gains an ellipsis 'Rule Actions' menu next to the
  checkmark holding Disable/Enable Rule and destructive Delete Rule;
  the red form rows are removed
- Tests pin the checkmark to the navigation bar with its label and
  drive disable/delete through the menu; the swipe-to-reach
  workarounds are gone. 95 passing
- Spec §6 updated

SeveredUITests/RuleCreationUITests.swift

@@ -22,8 +22,11 @@ final class RuleCreationUITests: XCTestCase {
         XCTAssertEqual(app.staticTexts["ruleEditorTitle"].waitToAppear().label, "In the Zone")
         XCTAssertTrue(app.staticTexts["During this time"].exists)
 
-        // Hold to commit saves the rule and returns home.
-        app.buttons["commitRuleButton"].waitToAppear().tap()
+        // The confirmation checkmark lives in the navigation bar and carries
+        // a descriptive accessibility label.
+        let commit = app.navigationBars.buttons["commitRuleButton"].waitToAppear()
+        XCTAssertEqual(commit.label, "Add Rule")
+        commit.tap()
         app.buttons["ruleCard-In the Zone"].waitToAppear()
         XCTAssertFalse(app.element("emptyRulesCard").exists)
     }