Docs updates for E/A#97308 opening a single expense from a report preview

[MelvinBot]

Explanation of Change

Help site follow-up for #97308, which changed what happens when you click or tap an expense card in a multi-expense Report Preview carousel: the expense you pressed now opens instead of the parent report.

The only help site article that covers report previews is docs/articles/new-expensify/reports-and-expenses/Getting-Started-with-the-Spend-Page.md. It described what a report preview shows ("Up to 10 expense previews", "Carousel navigation", "+X more link if there are over 10 expenses") but never described what pressing a card does, so it did not need a correction — it needed the missing behavior added.

This PR adds it:

• How to open a single expense from a report preview — pressing a card opens that expense in the right-hand panel with its report behind it, and back returns to the report and then the workspace chat.
• Two cases where the report opens instead: a preview with only one expense, and the View button (which always opens the report).
• How to move between expenses on a report — the previous and next arrows in the expense header step through every expense on the report in the order the report shows, including expenses beyond the cards the carousel renders.
• An offline note: an expense deleted while offline keeps its card in the carousel until you reconnect; pressing that card opens the report, and the arrows skip it.
• An FAQ entry for the likely support question, "Why did clicking an expense card open the whole report?"

Verified against the live UI on web before writing, so the labels match exactly:

• The report preview action button that opens the report is View (capital V, rest lowercase) — sits next to the green Approve button.
• Clicking an expense card opened the individual expense ($25.00 for Coffee Shop), not the parent report.
• The previous/next controls are unlabeled chevron icons in the expense header — they expose no aria-label and no hover tooltip, so the article describes them as "the previous and next arrows in the expense header" rather than inventing a label. The previous arrow is disabled on the first expense and the next arrow on the last.
• The +X more link and the 10-card cap in the existing article are still correct (MAX_PREVIEWS_NUMBER = 10), so those lines were left alone.

Written against docs/HELPSITE_NAMING_CONVENTIONS.md, docs/HELP_AUTHORING_GUIDELINES.md, and docs/TEMPLATE.md: both new headings are task-based ## headings starting with an action verb, no ### or deeper, button names bolded in the UI's exact capitalization, and the new FAQ entry is phrased as a user question. The article's pre-existing structure (its multiple # headings and noun-only section titles) was left untouched to keep this diff scoped to the behavior change.

Fixed Issues

$ #91042
PROPOSAL:

Tests

// TODO: The human co-author must fill out the tests you ran before marking this PR as "ready for review".
// This PR only changes markdown under docs/articles, so there is no app behavior to test — confirming the rendered article reads correctly is the check that matters.

• Verify that no errors appear in the JS console

Offline tests

QA Steps

// TODO: The human co-author must fill out the QA tests you ran before marking this PR as "ready for review", or add "[No QA]" to the title.
// Documentation-only change to a help site article — no app code is touched.

• 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 comments were added to code that is not self explanatory
  • 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 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)
• 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)
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
• If new assets were added or existing ones were modified, I verified that:
  • The assets are optimized and compressed (for SVG files, run npm run compress-svg)
  • 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.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• 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.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• 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

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

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@wildan-m, please review the files changed and confirm they reflect the current behavior. Then post a new comment saying @MelvinBot mark this PR as ready for review.