DSH session-title plugin

Key features

• Zero intrusionidentical to the official first-prompt-llm logic (first human message, streaming generation, fallback on failure) — only the prompt changes
• New titles onlyexisting sessions keep their stored titles
• Auto take-overmutually exclusive with the official plugin
• on load it shuts the official provider down and registers itself, so exactly one title generator stays active
• Fail-safeon model error, timeout, or empty output, it falls back to the official deterministic fallback title