Overhaul Feynman harness: streamline agents, prompts, and extensions

Remove legacy chains, skills, and config modules. Add citation agent,
SYSTEM.md, modular research-tools extension, and web-access layer.
Add ralph-wiggum to Pi package stack for long-running loops.

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

prompts/draft.md

@@ -4,18 +4,8 @@ description: Turn research findings into a polished paper-style draft with equat
 Write a paper-style draft for: $@
 
 Requirements:
-- Prefer the `writer` subagent when the draft should be produced from already-collected notes, and use `verifier` first if the evidence still looks shaky.
-- Ground every claim in inspected sources, experiments, or explicit inference.
-- Use clean Markdown structure with LaTeX where equations materially help.
-- Include at minimum:
-  - title
-  - abstract
-  - problem statement
-  - related work
-  - method or synthesis
-  - evidence or experiments
-  - limitations
-  - conclusion
-- If citations are available, include citation placeholders or references clearly enough to convert later.
-- Add a `Sources` appendix with direct URLs for all primary references used while drafting.
+- Use the `writer` subagent when the draft should be produced from already-collected notes, then use the `citation` subagent to add inline citations and verify sources.
+- Include at minimum: title, abstract, problem statement, related work, method or synthesis, evidence or experiments, limitations, conclusion.
+- Use clean Markdown with LaTeX where equations materially help.
 - Save exactly one draft to `papers/` as markdown.
+- End with a `Sources` appendix with direct URLs for all primary references.