[Draft] Display Show history button in Concierge side panel on native

[MelvinBot]

Explanation of Change

This is a draft PR sharing the proposed code diff for issue #89571 so the C+ team can test the changes ahead of approval.

The native Concierge entry-points (SidePanelButton, useOpenConciergeAnywhere) bypass the side-panel flow and open Concierge as a regular report screen. Because <SidePanel/> is never mounted on native (RootNavigatorExtraContent/index.native.tsx returns null), the IsInSidePanelContext.Provider never executes, useIsInSidePanel() always returns false, and ShowPreviousMessagesButton early-returns.

Changes:

• Mount <SidePanel/> on native via RootNavigatorExtraContent/index.native.tsx (mirroring the web variant). The component self-guards on sidePanelNVP, so it is inert until openSidePanel() is called.
• Delegate SidePanelButton/index.native.tsx to SidePanelButtonBase, so the help button calls openSidePanel() like web.
• Align useOpenConciergeAnywhere/index.native.tsx with the web variant (openSidePanel() + isInSidePanel: true).
• Pass shouldUseModalPaddingStyle={false} to the native SidePanelModal to remove double padding between Modal and ReportScreen (as noted by paulnjs in the issue thread).

Context for reviewers: dukenv0307 flagged in the issue that PR #76277 intentionally removed the native side panel due to edge cases, and mhawryluk confirmed the mobile implementation was deferred until the feature proved useful on web. Mounting <SidePanel/> on native re-enables that infrastructure. Please verify whether re-introducing it is desired before merging.

Fixed Issues

$ #89571
PROPOSAL: #89571 (comment)

Tests

1. Sign in to an account that has a long Concierge history (prior sessions with messages).
2. Tap the Concierge help button (top-right) on Android or iOS native.
3. Verify Concierge opens inside a right-docked side panel (not as a full-screen report).
4. Verify the "Show history" button appears at the top of the Concierge thread.
5. Tap "Show history" and verify older messages from prior sessions load.
6. Close the side panel (back button on Android / swipe-right on iOS) and re-open it; verify the session resets and only the new session messages are visible until "Show history" is tapped again.
7. From the search router on native, trigger the "Ask Concierge" flow and verify Concierge opens in the side panel.

• Verify that no errors appear in the JS console

Offline tests

Same as Tests, performed offline. Verify the side panel opens, the empty list renders, and no errors appear.

QA Steps

Same as Tests.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above

Screenshots/Videos

Android: Native

iOS: Native

MacOS: Chrome / Safari

[codecov]

Codecov Report

✅ Changes either increased or maintained existing code coverage, great job!

Files with missing lines	Coverage Δ
...igation/RootNavigatorExtraContent/index.native.tsx	100.00% <100.00%> (ø)
...ponents/SidePanel/SidePanelButton/index.native.tsx	100.00% <100.00%> (ø)
...ponents/SidePanel/SidePanelModal/index.android.tsx	0.00% <ø> (ø)
.../components/SidePanel/SidePanelModal/index.ios.tsx	0.00% <ø> (ø)
...rc/hooks/useOpenConciergeAnywhere/index.native.tsx	66.66% <60.00%> (+66.66%)	⬆️
... and 225 files with indirect coverage changes