docs(arch): realism leads the quality list; performance moves to the end

Owner decision: prioritise realism, keep the performance target but put it last.
Re-applied on a branch after the first attempt landed directly on main (reverted
there; see b8209ce).

- Quality goals (01 + combined architecture.md): 1 visual realism, 2 geographic
  fidelity, 3 walkability/usability, 4 reproducibility/portability, 5 provenance,
  6 performance efficiency.
- Quality requirements (10 + combined) reordered to match, with two realism
  requirements added (a façade reads like the photographs; placement within ~1 m)
  and the scenarios renumbered so QS-1 is the reference comparison, QS-9 the frame
  rate.
- Guard on both documents so the order cannot become an excuse: performance is a
  floor, not a preference - 60 FPS at 1440p without frame generation must be met at
  every release; if realism cannot fit, cut the realism scope deliberately and
  record it, never the frame rate. Walkability outranks realism in one direction: a
  block you fall through is not a demo.
- Solution strategy and 'quality achievement' lead with realism and describe
  performance as a budget, not a driver.
- Docs/release-checks.md: the performance check is the last section and the per-
  version check list now opens with realism and closes with performance.
- ROADMAP gains a 'Quality priority' section; AGENTS.md gains the tie-break rule
  beside the existing scope-cutting rule.

Docs/Architecture/01_introduction_and_goals.md

@@ -20,11 +20,14 @@ Full requirements and progress are in [TODO.md](../../TODO.md); version directio
 
 | Priority | Quality Goal | Scenario |
 | --- | --- | --- |
-| 1 | **Performance efficiency** | 60 FPS at 2560×1440 on RTX 5070 Ti, documented preset, no frame generation |
-| 2 | **Terrain walkability** | Zero raycast holes across both sidewalks and the carriageway (84-sample transect passes) |
-| 3 | **Geographic fidelity** | Building placement, street scale, and façade identity match reference photography |
+| 1 | **Visual realism** | Renders read as the reference photographs: façade identity, proportion, material and light — judged side by side, shot against photo |
+| 2 | **Geographic fidelity** | Building placement and street scale match the measured data and the photographs |
+| 3 | **Terrain walkability** | Zero raycast holes across both sidewalks and the carriageway (84-sample transect passes) |
 | 4 | **Build reproducibility** | Fresh checkout + documented engine path produces a runnable Linux build |
 | 5 | **Provenance** | Every committed asset has recorded provenance |
+| 6 | **Performance efficiency** | 60 FPS at 2560×1440 on RTX 5070 Ti, documented preset, no frame generation |
+
+**How the order is used.** It decides trade-offs. When realism and performance disagree, realism wins and the cost is paid — but never by silently shipping a frame rate below the floor. The 60 FPS figure is a **budget that must still be met**, so the response to "realism costs too much frame time" is to cut the realism feature deliberately, record the cut, and keep the floor — not to let frames slip. Walkability outranks realism in one direction only: a beautiful block the player falls through is not a demo.
 
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