Add multi-turn Paper Finder support with session management

[Grishezz]

Motivation

The Paper Finder backend supports multi-turn conversations — follow-up messages refine the search, explore new angles, or ask clarifying questions while maintaining full conversational context. This PR adds CLI support for that capability, replacing the previous single-shot find-and-report skills with a unified literature-understanding skill (built-in SQA to follow soon)

Summary

• Unified literature-understanding skill replacing find-literature and literature-report — covers search, follow-up, report generation, and Semantic Scholar lookups in a single skill with full JSON schema documentation
• Session-based artifact storage with human-readable folders under ~/.asta/literature/sessions/, an index.json for O(1) thread lookup, and per-turn results files
• followup command for conversational follow-ups within an existing search thread
• Agent text response support — the client polls for the agent's text response first, then checks once for a new widget
• threads, show, export commands for listing sessions, inspecting thread state, and exporting results to JSON/BibTeX/CSV

Example usage:
2026-03-11-173228-find-recent-papers-about-automated-poetry-translat.txt

[rodneykinney]

Supporting multi-turn was closer than I realized. Very cool!

As I said in the meeting, I want to preserve the ability to perform paper retrieval and report-writing independently, mostly for BYO pdfs. I'm open to many possible implementations, but here is what comes to my mind:

• Keep the existing literature find command
• I will add a literature summarize sub-command that calls the SQA API, replacing the current literature-report skill
• Add a literature interactive sub-command for multi-turn interactions with Paper Finder
  • This should be exposed to the agent as an MCP tool
  • The CLI actually launches a local MCP server
• Add literature interactive --resume flag to resume past sessions
  • Let the CLI manage session state and exports instead of putting it into the skill instructions