[coneilen]

Summary

Fix the C8R s-tabs-many-first failure by deriving the actual contiguous visible tab roster and using an exact stable-ID bridge before reacquiring and selecting the first tab. The product/provider contract is unchanged: hidden overflow tabs remain unpublished, tab names and IDs remain exact, and tab rows do not claim the sidebar-only ScrollItem pattern.

Changes

• Derive visible tab indexes from owned stable AutomationIds instead of assuming a ten-tab window.
• Bridge through the nearest visible tab edge, reacquire the UIA roster, and invoke the exact requested tab ID without extending action deadlines.
• Preserve strict refusal coverage for missing, foreign, duplicate, out-of-order, misnamed, wrongly selected, offscreen, and genuinely unavailable elements.
• Record the exact failed lease/job/manifest/fixture evidence in the matched-tab contract and document the overflow route.

Test plan

RED: pwsh -NoProfile -File Tools\windows\Tests\UiCaptureDriver.Tests.ps1 -MatchedScenarioContractOnly -ScratchRoot .build\c8r-many-tabs-red2 -> 6/8; s-tabs-many-first failed UIA element 'Shell' did not become available before the reserved deadline.
GREEN: pwsh -NoProfile -File Tools\windows\Tests\UiCaptureDriver.Tests.ps1 -MatchedScenarioContractOnly -ScratchRoot .build\c8r-many-tabs-green5 -> 8/8 passed.
REGRESSION: UiCaptureDriver D:\gcf3; real-zmx D:\gcr3; ValidationRunner; validate.ps1 -Task hardening -> 182/182, 185/185, 166/166 plus nested 182/182, and hardening 3/3 passed; no capture or lease used.

Additional checks:

• PowerShell parser passed for all changed scripts.
• git diff --check passed.
• git ls-files --eol reported LF for all changed files.
• The real-zmx run used immutable C:\e8\runtime\zmx.exe SHA-256 65E585375017EB2344655DAF2014AE8B6C5015923A0B3803C3890C83D4A1F702.

Checklist

• I have read the Contributing Guidelines
• I have signed off my commits (git commit -s) per the DCO
• Tests pass locally (make test)
• Code follows the existing style (make check)
• I added the test/contract before the implementation and observed the intended RED failure

make test and make check are macOS gates and were not run for this Windows-only capture-tooling change; the Windows validation matrix above passed.