docs: prune stale planning artifacts

[mldangelo-oai]

Summary

• remove one-shot format-gap plans for CoreML, MXNet, TensorFlow MetaGraph, and TorchServe MAR now that scanner files, routing, and tests exist
• remove the dated CVE PR plan that was superseded by implemented scanner coverage and the broader CVE gap analysis
• rename the scanner CVE gap analysis to a stable canonical path and link the surviving audit docs from maintainer/agent references

Cleanup audit notes

• Format-gap plans were introduced during the March 2026 scanner implementation work; they became orphaned once the corresponding scanners/tests landed and later registry metadata was centralized.
• The March 20 CVE PR plan became stale after Keras, TorchServe MAR, and MXNet coverage landed and the April CVE gap analysis captured remaining research work.
• The repo correctness ledger remains useful, so this PR rewires it from architecture docs and updates its stale PR-status section.

QA

• npm ci --ignore-scripts
• npx prettier --write "docs/**/*.md"
• npx prettier --check "docs/**/*.md"
• git diff --check
• rg -n "format-gap-plans|cve-gap-pr-plan-2026-03-20|scanner-cve-gap-analysis-2026-04-11" .