Share sheet: ask to unlock on every gated action, like the app

The sheet remembered one unlock for its whole lifetime, so later account picks
and hidden toggles skipped Face ID. Each switch / each turning-on of hidden
folders now prompts again; one action needing both is a single prompt.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/RunnerTests/RunnerTests.swift

@@ -217,6 +217,55 @@ class RunnerTests: XCTestCase {
     XCTAssertTrue(rules(master: true, switching: true, hidden: true) == (true, true))
   }
 
+  // Which actions in the share sheet ask to unlock - and how many prompts.
+
+  private func lockedAccounts(switching: Bool, hidden: Bool) -> SharedAccounts {
+    SharedAccounts(
+      accounts: [account("alice"), account("bob")], activeId: "alice",
+      loginLockEnabled: false, lockAccountSwitching: switching, lockHiddenFiles: hidden)
+  }
+
+  func testChoosingTheActiveAccountWithoutHiddenFoldersNeverPrompts() {
+    let shared = lockedAccounts(switching: true, hidden: true)
+    let needs = shared.unlockNeeds(choosing: account("alice"), showing: .hide)
+    XCTAssertEqual(needs, SelectionUnlock(switchesAccount: false, showsHidden: false))
+    XCTAssertFalse(needs.needsPrompt)
+  }
+
+  func testChoosingAnotherAccountPromptsEveryTime() {
+    let shared = lockedAccounts(switching: true, hidden: false)
+    // No unlock is remembered: the same choice asks again on every call.
+    for _ in 0..<3 {
+      XCTAssertTrue(shared.unlockNeeds(choosing: account("bob"), showing: .hide).needsPrompt)
+    }
+    XCTAssertFalse(
+      lockedAccounts(switching: false, hidden: false).unlockNeeds(choosing: account("bob"), showing: .hide).needsPrompt)
+  }
+
+  func testSwitchPlusHiddenFoldersIsOnePromptThatCoversBoth() {
+    let needs = lockedAccounts(switching: true, hidden: true)
+      .unlockNeeds(choosing: account("bob"), showing: .include)
+    XCTAssertEqual(needs, SelectionUnlock(switchesAccount: true, showsHidden: true))
+    XCTAssertTrue(needs.needsPrompt)
+  }
+
+  func testHiddenFoldersAloneOnTheActiveAccountPromptsForHidden() {
+    let needs = lockedAccounts(switching: true, hidden: true)
+      .unlockNeeds(choosing: account("alice"), showing: .only)
+    XCTAssertEqual(needs, SelectionUnlock(switchesAccount: false, showsHidden: true))
+  }
+
+  func testOnlyTurningHiddenFoldersOnAsksToUnlock() {
+    let locked = lockedAccounts(switching: false, hidden: true)
+    XCTAssertTrue(locked.needsUnlockToChangeHidden(from: .hide, to: .only))
+    XCTAssertTrue(locked.needsUnlockToChangeHidden(from: .hide, to: .include))
+    XCTAssertFalse(locked.needsUnlockToChangeHidden(from: .include, to: .hide), "hiding again never asks")
+    XCTAssertFalse(locked.needsUnlockToChangeHidden(from: .only, to: .include), "only <-> all never asks")
+    XCTAssertFalse(
+      lockedAccounts(switching: false, hidden: false).needsUnlockToChangeHidden(from: .hide, to: .include),
+      "no lock set, no prompt")
+  }
+
   // MARK: - TransferBatchStore
 
   func testBatchSummaryFiresOnlyOnTheLastFile() {