Fix UI searches continuing past their timeout

[sbroenne]

Summary

Closes #253.

• Use one deadline across ui_find and appear/disappear wait retries and accessibility-tree scans.
• Do not start a final full scan at or after the deadline; stop between provider operations in matching, modal-dialog lookup, framework detection, element conversion, identity lookup, child enumeration, and fallback passes.
• Return an explicit timeout when a scan is unfinished rather than claiming absence, uniqueness, or successful disappearance.
• Preserve last-scan diagnostics and distinguish a missing window/dialog from a missing element, including whitespace-padded dialog scopes.
• Reuse detected framework information for diagnostics where available.
• Keep timeoutMs=0 as one node-bounded scan without a time deadline; document that Windows accessibility calls already running can still overrun the budget.

This addresses confirmed timeout-policy problems. It does not establish why the originally reported Install button was missed.

Validation

• Build succeeds without warnings after merging current main.
• 959 unit tests pass.
• 62 targeted Windows integration tests pass, covering deadlines, disappearance, dialog scopes, uniqueness, and node budgets.
• Added deterministic provider-call and slow-traversal regressions plus real queued-search timeout tests for find and disappearance.
• Updated the existing disappearance timeout test to distinguish completed observations from interrupted scans, while asserting failure, timeout type, elapsed budget, and absence of success items.
• Node-budget-only MCP tests explicitly use timeoutMs=0 so they test the 2,000-node limit independently of machine speed.

Full Windows integration validation runs through the pull request workflow.

[Copilot]

Copilot review overview

🟡 Changes recommended

Several auxiliary UIA traversals still make multiple provider calls without deadline checks, allowing searches to continue after timeout.

Review effort: Balanced
Findings: 5

Open (5)

• Make condition matching deadline-aware · New
• Normalize scope before active dialog diagnostics · New
• Make active dialog lookup deadline-aware · New
• Bound framework detection with deadline checks · New
• Add deadline checks during child enumeration · New

What changed in this PR

Introduces shared deadlines across UI searches, retries, and tree traversal while improving timeout diagnostics and documentation.

Changes:

• Stops retries and bounded traversal when deadlines expire.
• Preserves timeout diagnostics and distinguishes unfinished searches.
• Adds unit and integration coverage for deadline behavior.

File	Description
FEATURES.md	Documents timeout semantics.
UIAutomationDiagnostics.cs	Clarifies timeout configuration.
BoundedSearchTraversal.cs	Adds traversal deadline checks.
UIAutomationService.Find.cs	Applies shared deadlines and diagnostics.
UIAutomationService.Tree.cs	Shares deadlines across wait scans.
UIFindTool.cs	Documents find timeout behavior.
UIWaitTool.cs	Documents wait timeout behavior.
BoundedSearchTraversalTests.cs	Tests traversal interruption.
FindDeadlineTests.cs	Tests retry and diagnostic semantics.
UIAutomationAdvancedSearchTests.cs	Updates deadline integration expectations.
UIFindToolIntegrationTests.cs	Tests queued-search expiration.

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