Fix "tool undefined completed" accessibility announcement in chat

[Copilot]

When a chat tool completes but has no confirmationMessages.title, screen readers were announcing "Tool undefined completed" instead of providing meaningful information.

Root Cause

The accessibility provider was attempting to access the .value property on an undefined title object:

// Before: This would result in "Tool undefined completed"
typeof invocation.confirmationMessages?.title === 'string' 
  ? invocation.confirmationMessages?.title 
  : invocation.confirmationMessages?.title.value  // ← .value on undefined

Solution

Added proper null checks and fallback logic to handle all title scenarios:

// After: Proper validation with fallback to toolId
const titleObj = invocation.confirmationMessages?.title;
let title = '';
if (typeof titleObj === 'string' && titleObj.trim()) {
    title = titleObj;
} else if (titleObj && typeof titleObj === 'object' && 'value' in titleObj && titleObj.value && titleObj.value.trim()) {
    title = titleObj.value;
} else {
    // Fallback to toolId if no valid title
    title = invocation.toolId;
}

The fix now handles:

• ✅ Undefined confirmationMessages
• ✅ Undefined title property
• ✅ Empty or whitespace-only titles
• ✅ Valid string titles
• ✅ Valid MarkdownString titles with .value property
• ✅ Graceful fallback to toolId when needed

Testing

Added comprehensive test cases covering all scenarios to prevent regressions.

Fixes #251439.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• electronjs.org
  • Triggering command: node-gyp (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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