Add device-code auth fallback to Connect-FabricAccount

[Theragus]

Pull Request

Pull Request (PR) description

Connect-FabricAccount can fail silently in some terminal hosts when interactive/broker (WAM) sign-in can't display its account picker — e.g. Warp on Windows, which doesn't expose a window handle for WAM to parent its UI to. Connect-AzAccount throws instead of showing anything, and that failure previously propagated straight out of Connect-FabricAccount with no recovery path.

This PR adds an automatic fallback to device code authentication when the interactive sign-in attempt fails, plus a -UseDeviceAuthentication switch for explicit opt-in.

No related issue is linked — the underlying WAM failure turned out to be intermittent/hard to reproduce on demand across different terminal hosts (Warp, Git Bash/mintty both completed sign-in fine via Az.Accounts' own browser fallback once retried), so this is a proactive resiliency fix rather than a direct fix for a filed bug.

Added

• Added -UseDeviceAuthentication switch to Connect-FabricAccount to force device code authentication instead of the interactive broker/browser flow

Fixed

• Connect-FabricAccount now automatically falls back to device code authentication when interactive/broker (WAM) sign-in fails, e.g. in terminal hosts such as Warp on Windows where the account picker cannot render

Task list

• The PR represents a single logical change. i.e. Cosmetic updates should go in different PRs.
• Added an entry under the Unreleased section of in the CHANGELOG.md as per format.
• Local clean build passes without issue or fail tests (build.ps1 -ResolveDependency -Tasks build, test).
• Comment-based help added/updated.
• Examples appropriately added/updated.
• Unit tests added/updated..
• Integration tests added/updated (where possible).
• Documentation added/updated (where applicable).
• Code follows the contribution guidelines.

Notes on unchecked items

• Local clean build/test: Invoke-Pester ./tests/Unit/Connect-FabricAccount.Tests.ps1 passes 10/10 against the built module. I did not check this box because the full suite (./build.ps1 -Tasks build,test) has pre-existing failures unrelated to this change: Integration tests require a live Fabric session/capacity (not available in this environment), and Get-FabricWorkspaceUser.Tests.ps1 has a pre-existing mandatory-parameter mismatch unrelated to this PR.
• Integration tests: not added — this change only affects the interactive auth failure/retry path, which isn't practical to exercise as a non-interactive integration test.
• Documentation: docs/en-US/Connect-FabricAccount.md was intentionally left untouched. ./build.ps1 -Tasks Generate_help_from_built_module in my environment picks up a pre-installed higher-version copy of FabricTools instead of the local build, which produces an unrelated repo-wide diff across all cmdlets' docs instead of just this one. Happy to add a manually-written doc update for just Connect-FabricAccount if maintainers would like one included before merge.

[NowinskiK]

Thanks for your contribution, @Theragus. Please look at the build errors and fix them if you can.