Add resizable windows and sentence-by-sentence speech option

[Copilot]

Enables window resizing for the Settings dialog and adds a user option to display speech sentence-by-sentence instead of in one long bubble.

Changes

Resizable Windows

• Changed SettingsForm from FixedDialog to Sizable with minimum size constraint
• Added anchors to tab control and dialog buttons for proper resize behavior

Sentence-by-Sentence Speech

• Added TruncateSpeech setting (default: false) with UI toggle in Voice tab
• Implemented SplitIntoSentences() using regex pattern (?<=[.!?])\s+|(?<=\.\.\.)\s*
• Added SpeakSentences() to queue each sentence separately to MS Agent

// When truncation is enabled, text is split and queued per sentence
if (_settings.TruncateSpeech)
{
    var sentences = AppSettings.SplitIntoSentences(cleanText);
    _agentManager.SpeakSentences(sentences);  // Each sentence gets its own bubble
}
else
{
    _agentManager.Speak(cleanText);  // Original behavior
}

Note: Simple sentence splitting may not handle all edge cases (e.g., abbreviations like "Dr.", decimal numbers).

Original prompt

Make the windows resizable. Add an option to truncate speech, so that instead of it all being one long speech bubble, it will go sentence by sentence

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