Fix addDelegate: stale closure, first-time user guard, and error handling

[MelvinBot]

Explanation of Change

This PR fixes three issues in the addDelegate function in src/libs/actions/Delegate.ts that contribute to the copilot invite succeeding at the API level but not persisting the delegate relationship on the frontend:

1. Fix early-return guard for first-time delegate users: The guard if (!delegatedAccess?.delegates) silently aborted when delegates was undefined, which happens for users who have never configured delegates. Changed to only abort when delegatedAccess itself is missing, treating undefined delegates as an empty array.

2. Fix stale closure overwriting server data in successData: The successDelegateData() function rebuilt the entire delegates array from the closure-captured snapshot taken when addDelegate() was called. Since the Onyx update pipeline applies server onyxData first and then merges successData on top, this stale array could overwrite the authoritative delegate list returned by the server. Removed the delegates array from successData entirely so the server's response stands.

3. Add error handling to failureData: The failureData did not include errorFields.addDelegate[email], so when the backend returned a non-200 response, the delegate entry persisted with pendingAction: ADD but no error was shown to the user. Added the error field so users see a proper error message on failure.

Fixed Issues

$ #82446
PROPOSAL: #82446 (comment)

Tests

1. Navigate to Settings > Security > Copilot: Delegated access
2. Add a copilot by entering an email and selecting a role
3. Enter the magic code when prompted
4. Verify the delegate is added successfully and appears in the copilot list
5. Verify that if the API returns an error, an error message is displayed to the user
6. Verify that for a first-time delegate user (no existing delegates), the flow works correctly without silently failing

• Verify that no errors appear in the JS console

Offline tests

1. Start the copilot add flow while online
2. Go offline before submitting the magic code
3. Verify the optimistic delegate entry appears with a pending state
4. Go back online and verify the delegate resolves correctly or shows an error

QA Steps

1. Log in as a user who has never added a copilot before (no existing delegates)
2. Go to Settings > Security > Copilot: Delegated access
3. Add a copilot by entering another user's email
4. Select a role (Full or Limited) and enter the magic code
5. Verify the copilot is added and appears in the delegates list
6. Verify no errors appear in the JS console

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
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  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
    • If any non-english text was added/modified, I used JaimeGPT to get English > Spanish translation. I then posted it in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
  • I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
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  • I verified the JSDocs style guidelines (in STYLE.md) were followed
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
• I verified any variables that can be defined as constants (ie. in CONST.ts or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
• If any new file was added I verified that:
  • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
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  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
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  • The assets load correctly across all supported platforms.
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
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• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
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• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

Android: Native

N/A - Logic-only change, no UI modifications

Android: mWeb Chrome

N/A - Logic-only change, no UI modifications

iOS: Native

N/A - Logic-only change, no UI modifications

iOS: mWeb Safari

N/A - Logic-only change, no UI modifications

MacOS: Chrome / Safari

N/A - Logic-only change, no UI modifications

[MelvinBot]

I created this PR from an upstream branch since I don't have push access to your fork.

To take ownership of this branch and be able to push updates, run:

git remote add upstream https://github.com/Expensify/App.git
git fetch upstream claude-fixDelegateAddPersistence
git checkout -b claude-fixDelegateAddPersistence upstream/claude-fixDelegateAddPersistence
git push -u origin claude-fixDelegateAddPersistence

Then you can close this PR and open a new one from your fork.

[codecov]

Codecov Report

❌ Looks like you've decreased code coverage for some files. Please write tests to increase, or at least maintain, the existing level of code coverage. See our documentation here for how to interpret this table.

Files with missing lines	Coverage Δ
src/libs/actions/Delegate.ts	31.48% <27.27%> (-0.16%)	⬇️
... and 11 files with indirect coverage changes