Async TTS and Enhanced Context-Aware AI Notifications

[Looted]

• Async TTS: Notification TTS generation and playback are now non-blocking (async), ensuring the terminal remains responsive while the agent speaks.
• Context-Aware AI: Enhanced AI message generation to include session context (last user goal, work summary, and error status) for more meaningful notifications.
• Sarcastic/Irony Tone: Updated default AI prompts to generate more concise, action-oriented, and sarcastically witty messages as requested.
• WSL2 Support: Added a note to README about WSL2 support and increased AI message limits.
• Tests: Updated tests to reflect new context injection logic and prompt expectations.

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PR created automatically by Jules for task 3599185859102748228 started by @Looted

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