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/review.md

@@ -7,6 +7,7 @@ topLevelCli: true
 Review this AI research artifact: $@
 
 Requirements:
+- Before starting, outline what will be reviewed and the review criteria (novelty, empirical rigor, baselines, reproducibility, etc.). Present the plan to the user and confirm before proceeding.
 - Spawn a `researcher` subagent to gather evidence on the artifact — inspect the paper, code, cited work, and any linked experimental artifacts. Save to `research.md`.
 - Spawn a `reviewer` subagent with `research.md` to produce the final peer review with inline annotations.
 - For small or simple artifacts where evidence gathering is overkill, run the `reviewer` subagent directly instead.