fix: batch merge of TUI fixes (PRs #2782-#2792)

Merged fixes for multiple TUI issues:
- #2782: Ctrl+W delete word backward
- #2783: Insert key toggle
- #2784: Double-click word selection
- #2785: Terminal state corruption on suspend/resume
- #2786: Windows ANSI escape sequences
- #2788: Async task/HTTP cancellation on Ctrl+C
- #2789: Graceful shutdown for WebSocket/HTTP
- #2791: Child process environment sanitization
- #2792: TUI streaming output optimization

Based on PR #289 (fix/bounty-batch-2782-2792)

Author: factorydroid