[No QA] Docs updates for E/A#95217 document marking a chat or message as unread

[MelvinBot]

Explanation of Change

Help site follow-up to Show New message marker when a user marks their own message as unread, which fixed the green New line not appearing when a member marks their own message as unread.

No existing article was made inaccurate by that PR — the Mark as unread / Mark as read message and chat actions were never documented on the help site at all. This PR adds a single new article covering that workflow:

docs/articles/new-expensify/chat/Mark-a-Chat-or-Message-as-Unread.md

It documents:

• How to mark an individual message as unread (web: hover, then the three dots (⋮); mobile: long-press).
• How to mark a whole chat as unread or read from the Inbox, and that Mark as read is available for a whole chat only.
• What happens after marking a message as unread — the message and everything after it counts as unread, the chat is bold in the Inbox and counted in the Unread tab, and a green New line appears above the marked message.
• That marking your own message as unread works the same way as marking someone else's — the behavior PR 95217 fixed.
• That read state is personal and never notifies anyone else.

Labels and feature names were taken from the product source rather than paraphrased: reportActionContextMenu.markAsUnread = Mark as unread, reportActionContextMenu.markAsRead = Mark as read, and the marker itself renders common.new = New. The Unread tab name matches the existing Navigating New Expensify article.

Authored against docs/HELPSITE_NAMING_CONVENTIONS.md, docs/HELP_AUTHORING_GUIDELINES.md, and docs/TEMPLATE.md: one workflow, a single # title plus # FAQ, task-based ## headings only, YAML metadata with internalScope, bolded UI labels, separate Web/Mobile steps, one screenshot placeholder with a stated purpose, and one relative cross-link. ./.github/scripts/createDocsRoutes.sh passes, so no _routes.yml change is needed.

One item needs your confirmation before this ships: the FAQ answer "Why is the green New line gone when you return to a chat?" states that leaving the chat and coming back, or reloading, clears the line. That matches the merged code (openReport clears manuallyMarkedUnreadReportActionID on a return trip or a cold start), but I could not verify it in a live session — the per-message hover menu never mounted in the headless web test environment, so the action could not be triggered. Please confirm or correct that answer.

Fixed Issues

$
PROPOSAL:

Tests

// TODO: The human co-author must fill out the tests you ran before marking this PR as "ready for review"
// Please describe what tests you performed that validates your changed worked.

• Verify that no errors appear in the JS console

Offline tests

N/A — documentation only, no app code is changed.

QA Steps

// TODO: The human co-author must fill out the QA tests you ran before marking this PR as "ready for review".
// Please describe what QA needs to do to validate your changes and what areas do they need to test for regressions.

• 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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@Ollyws, 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.

[OSBotify]

A preview of your ExpensifyHelp changes have been deployed to https://b1bdbbdc.helpdot.pages.dev ⚡️

Updated articles:

• articles/new-expensify/chat/Mark-a-Chat-or-Message-as-Unread