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/deepresearch.md

@@ -40,6 +40,8 @@ Write the plan to `outputs/.plans/deepresearch-plan.md` as a self-contained arti
 
 Also save the plan with `memory_remember` (type: `fact`, key: `deepresearch.plan`) so it survives context truncation.
 
+Present the plan to the user and ask them to confirm before proceeding. If the user wants changes, revise the plan first.
+
 ## 2. Scale decision
 
 | Query type | Execution |
@@ -107,6 +109,8 @@ Detailed findings organized by theme or question.
 Unresolved issues, disagreements between sources, gaps in evidence.
 ```
 
+When the research includes quantitative data (benchmarks, performance comparisons, trends), generate charts using `pi-charts`. Use Mermaid diagrams for architectures and processes. Every visual must have a caption and reference the underlying data.
+
 Save this draft to a temp file (e.g., `draft.md` in the chain artifacts dir or a temp path).
 
 ## 6. Cite