chore(bmad): migrate integration to Codex

[Roddygithub]

Summary

Phase 4 cleans up the existing BMAD integration while retaining the official
BMAD 6.11.0 framework and canonical skills.

• Regenerates the BMAD integration for Codex and records ides: [codex].
• Removes the obsolete OpenCode wrappers and configuration.
• Removes the Supermemory export and makes Supermemory non-operational and
  optional; repository documents and versioned checkpoints are durable memory.
• Strengthens AGENTS.md privacy rules for the private WvW/ corpus and marks
  historical planning material as non-authoritative.
• Adds BMAD framework checks for version 6.11.0, Codex-only integration, the
  expected 49 generated skills, and absence of active OpenCode configuration.
• Includes the sanitized, versioned Phase 4 checkpoint.

Validation

• uv run pytest tests/scripts/test_bmad_framework.py — 7 passed
• uv run ruff check tests/scripts/test_bmad_framework.py — passed
• BMAD configuration and customization resolvers — passed
• git diff --check HEAD — passed
• Independent final review — CLEAN

Scope

No application behavior, API, data, CI, GitHub configuration, SPEC, or ADR
changes. The private WvW/ corpus and unrelated audit/EI artifacts are
excluded.