docs(architecture): make section pages canonical

MEMORY.md

@@ -13,7 +13,7 @@ Scope: facts and traps that cost time to establish. Planned work lives in [TODO.
 - **prettier 3.9.10** installed globally via npm (Node v24.20.0). Project config: `.prettierrc` (`proseWrap: never`, `tabWidth: 2`), `.prettierignore` (skips `Binaries/`, `*.uasset`, `.agents/`).
 - **Conversion chain:** `.adoc` → `asciidoctor -b docbook5` → `.xml` → `pandoc -f docbook -t gfm` → `.md` → `prettier --write`. Pandoc's built-in `asciidoc` reader cannot handle Asciidoctor tables or attributes — it must go through docbook5.
 - **Post-processing fixes:** glossary `cols="e,2e"` emphasis leaks italic into cell content (strip `*...*` wrapping), `®` from the R key binding becomes `(R)`, anchor IDs `{#...}` stripped, escaped quotes/brackets normalised.
-- **All `.adoc` files removed.** Markdown is the canonical format. Architecture doc lives in `Docs/Architecture/` as 13 section `.md` files + combined `architecture.md`.
+- **All `.adoc` files removed.** Markdown is the canonical format. Architecture documentation lives in `Docs/Architecture/` as `README.md`, twelve numbered section pages, and `about-arc42.md`.
 - All `.md` in the repo passes `prettier --check` (23 files formatted, `.agents/` excluded as vendored content).
 
 ## 2026-11-08 — QA branch merged; demo is walkable
@@ -423,7 +423,7 @@ Scope: facts and traps that cost time to establish. Planned work lives in [TODO.
 
 ## 2026-11-09 — quality priority flipped: realism first, performance last
 
-- Owner decision: realism leads; performance closes the quality list. Applied in `Docs/Architecture/01_introduction_and_goals.md`, `10_quality_requirements.md`, `04_solution_strategy.md`, the combined `architecture.md`, `Docs/release-checks.md` (performance section now last, with the reason), `ROADMAP.md` (a "Quality priority" section) and `AGENTS.md` (the tie-break rule next to the scope-cutting rule).
+- Owner decision: realism leads; performance closes the quality list. Applied in `Docs/Architecture/01_introduction_and_goals.md`, `10_quality_requirements.md`, `04_solution_strategy.md`, `Docs/release-checks.md` (performance section now last, with the reason), `ROADMAP.md` (a "Quality priority" section) and `AGENTS.md` (the tie-break rule next to the scope-cutting rule).
 - Ordering used: 1 visual realism, 2 geographic fidelity, 3 walkability/usability, 4 build reproducibility/portability, 5 provenance, 6 performance.
 - **Both revisions carry the same guard so the order cannot be used as an excuse:** performance is a _floor_, not a preference — 60 FPS at 1440p without frame generation must be met at every release, and if realism cannot fit, the realism scope is cut deliberately and recorded in `CHANGELOG.md`, never the frame rate. Walkability outranks realism in one direction: a block the player falls through is not a demo.