Replace placeholder MIP-3, MIP-4 and MIP-7 chat sources with reviewed facts #57

content/mips/mip-3.md, mip-4.md and mip-7.md still contain TODO(author) for status/specification and other sections. getKnowledgeBundle() loads these files into the chat context, and the public Markdown routes expose them. The MIP-12 correction in #56 does not fill these remaining source gaps.

The first upstream drift report also flags changes since the initial reviewed baseline. The pinned upstream comparison includes MIP-3's exceptional-halt wording, MIP-4 validation/gas clarification, and MIP-7's missing-selector rule. MIP-8 and MIP-12 status changed upstream too; the site already has separately sourced activation material for those two.

Approved scope:

• Replace the three placeholder Markdown documents with concise, accurate summaries of their canonical specifications. Include proposal status, exact source revision, review date, and the canonical discussion link.
• Cover the 8 MB call-frame memory limit and exceptional-halt gas behavior for MIP-3; MIP-4's CALL-only precompile, exact calldata and failure semantics; and MIP-7's selector restrictions, undefined selectors and trailing EXTENSION byte behavior.
• Separate proposal status from network activation. Cite official activation evidence when available; otherwise say activation is unverified. Do not infer activation from a Final status.
• Test the actual knowledge bundle and Markdown routes for these facts and absence of placeholders. Preserve the MIP-8 and MIP-12 factual corrections.
• Review each of the five entries in upstream-sources.json against the linked diff and current content before advancing its hashes. Record the disposition for each MIP in the PR, including any remaining UI mismatch. Do not refresh hashes just to silence the checker; leave an entry flagged and link a follow-up if its content still needs work.

Keep this to source documents, their regression coverage and reviewed-source metadata. #52 owns the server's citation/prompt behavior, and #35 owns the MIP-4 interactive redesign.

Comment to claim and wait for maintainer approval before starting. One active claim per person across the pool.