docs(rfc): track r1-r3 replacements and defer r4 executor

[huangruiteng]

Summary

Track replacement-first progress in the RFC.

• Mark M6 as in progress with R1-R3 PRs (refactor(control-plane): render bootstrap steps through effect program #2955, refactor(control-plane): resolve turn result kind through effect turn #2956, refactor(control-plane): build scheduler commands through effect program #2957).
• Record the three real runtime replacements in the abstraction inventory.
• Explicitly defer R4 (ordered effect executor) until a real multi-step
  host/turn-driver caller exists.

No runtime behavior changes.

Validation

• docs-governance-smoke: passed.
• loopx canary premerge --from-git-diff: passed, self_merge_allowed=true,
  0 manual holds.
• Public boundary scan: passed.

Routing

• continuation-policy: independent_handoff
• excluded-agent: codex-quality-qualification
• claimed-by: codex-side-bypass

[huangruiteng]

Approval conclusion (author-owned PR; GitHub blocks formal self-approval)

Reviewed exact head cc9bed1. No blocking findings.

The RFC now records R1-R3 real replacements and defers R4 executor until a
real multi-step caller exists. Docs only, no runtime behavior changes.

Validation

• docs-governance-smoke: passed.
• loopx canary premerge --from-git-diff: passed, self_merge_allowed=true,
  0 manual holds.
• GitHub dependency-review on this head: pass. Python/build workflows are not
  triggered for a docs-only path change.
• Public boundary scan: passed.

Merge decision: approved after reviewer.