Add plan-confirm steps to all workflows, cite alphaXiv and Agent Computer, add visuals to writer

- Every workflow prompt now shows a plan and asks the user to confirm before executing
- /autoresearch asks for execution environment (local, branch, venv, cloud) and confirms before looping
- Writer agent and key prompts now generate charts (pi-charts) and diagrams (Mermaid) when data calls for it
- Cite alphaXiv and Agent Computer in README and website homepage
- Clear terminal screen before launching Pi TUI
- Remove Alpha Hub GitHub link in favor of alphaxiv.org

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

prompts/compare.md

@@ -7,8 +7,10 @@ topLevelCli: true
 Compare sources for: $@
 
 Requirements:
+- Before starting, outline the comparison plan: which sources to compare, which dimensions to evaluate, expected output structure. Present the plan to the user and confirm before proceeding.
 - Use the `researcher` subagent to gather source material when the comparison set is broad, and the `verifier` subagent to verify sources and add inline citations to the final matrix.
 - Build a comparison matrix covering: source, key claim, evidence type, caveats, confidence.
+- Generate charts with `pi-charts` when the comparison involves quantitative metrics. Use Mermaid for method or architecture comparisons.
 - Distinguish agreement, disagreement, and uncertainty clearly.
 - Save exactly one comparison to `outputs/` as markdown.
 - End with a `Sources` section containing direct URLs for every source used.