docs: record The Quiet Engine arc before MVP 5 (ADR-0044) and update the roadmap

[jasonssdev]

Summary

Records the owner's approval of "The Quiet Engine" arc (#1268) and its place on the roadmap.

• ADR-0044 — The Quiet Engine arc precedes Interoperability (Proposed). A named arc that cuts the decisions OpenKOS asks per source goes between MVP 4 and MVP 5. MVP numbers stay, so accepted ADRs that name later MVPs (ADR-0039) stay accurate, and delaying OKF export is accepted. The structural auto-merge class stays opt-in and off by default under ADR-0034; default-on would need a later superseding ADR backed by evidence. Event and Person are excluded from attach-at-ingest at first. The arc's product-metric bars are fixed in a pre-registration before it starts. Alternatives: renumbering as MVP 5, superseding ADR-0034 for default-on, including Person, building MVP 5 first.
• docs/roadmap.md: new section "The Quiet Engine — a named arc before MVP 5" (goal, deliverables in dependency order, exit criteria to be fixed in the pre-registration, out of scope, user outcome). MVP 5 and MVP 6 keep their content.
• AGENTS.md, README.md: name the arc as next, then MVP 5.

No accepted ADR is edited.

Related issue

Refs #1268

Type of change

• feat — new feature
• fix — bug fix
• docs — documentation only
• refactor — no behavior change
• test — tests only
• chore / ci — tooling, build, or CI
• Breaking change

How was this tested?

• tests/unit/test_adr_index.py (ADR status consistency) passes.
• ruff check, ruff format --check, mypy ., pytest --cov (96.46%), evals/run_self_tests.py (46/46) pass locally.

Checklist

• My commits follow Conventional Commits.
• I added or updated tests for the change.
• I updated docs where behavior, interfaces, or the knowledge model changed.
• Lint, format, type check, and tests pass locally (ruff, mypy, pytest).
• Output remains OKF-conformant and derived stores stay reconstructible from the bundle + sources.
• The change is consistent with the project's guiding principles (local-first, provenance, freshness, human-in-the-loop).