Docs updates for E/A#100678 Add DualEntry vendor matching help article

[MelvinBot]

Explanation of Change

Help site follow-up for Expensify/App#100678, which extended vendor matching to DualEntry (expense Vendor picker, workspace Vendors page, merchant rules, and vendor-name lookup).

The help site had no article covering vendor matching for DualEntry. The sibling articles for QuickBooks Online and Sage Intacct already exist, and a Rillet one is in flight in Expensify/App#100899, so this adds the matching DualEntry article and follows that structure.

New: docs/articles/new-expensify/connections/dualentry/Manage-Vendor-Matching-for-DualEntry.md

It documents the behavior introduced or changed by PR #100678:

• Who can use it — a configured DualEntry connection, with the feature still rolling out gradually (the vendorMatching beta gate in hasVendorFeature).
• Which vendors are available — DualEntry is the only vendor-matching source that scopes its list by subsidiary. getDualEntryVendors keeps active vendors that are either assigned to the connection's selected Subsidiary or not assigned to any subsidiary, so the article explains that scoping and what happens after a subsidiary change.
• Automatic matching, manual selection, and the Vendors page — merchant rule → merchant-name match → empty, plus the Concierge system message, the Vendor row on non-reimbursable expenses only, and Find vendor on the workspace Vendors page.
• Default vendor — the DualEntry export label is Default vendor for all company cards, which differs from the Default company card vendor label used by Rillet.
• Export fallback — expense vendor → Default vendor for all company cards → an auto-created Credit Card Misc vendor, which is reused and does not get written back into the workspace default. This matches the "Credit Card Misc fallback on export" test steps on Add DualEntry support for vendor matching #100678.
• Vendors that are no longer valid — the Vendor no longer valid expense error and the Vendor unavailable merchant rule display value.
• Precedence — PR Add DualEntry support for vendor matching #100678 places DualEntry last in the QuickBooks Online → Sage Intacct → Xero → Rillet → DualEntry order, so the article states that DualEntry vendors scope the Vendor field only when none of the others are configured, while the DualEntry export default always uses DualEntry vendors.

Updated: docs/articles/new-expensify/connections/dualentry/Configure-DualEntry.md — one cross-link from the export settings section to the new article.

The article is marked noindex: true / sitemap: false while the feature is beta-gated, matching the Rillet vendor matching article.

All UI labels were taken verbatim from src/languages/en.ts (workspace.dualEntry.*, workspace.moreFeatures.vendors.*, workspace.vendors.*, violations.inactiveVendor, workspace.rules.vendorUnavailable) and the navigation labels were checked against the live web build. Note that both the DualEntry connection and the Vendors row are beta-gated, so neither is visible on a standard account today.

Fixed Issues

$ https://github.com/Expensify/Expensify/issues/679020
PROPOSAL:

Tests

// TODO: The human co-author must fill out the tests you ran before marking this PR as "ready for review".

• 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 the title must include "[No QA]."

• 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
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• 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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@lakchote, 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.