ocs_doc_api: enrich + update all documentation (architecture flow diagram, guarantees, counts)

- ARCHITECTURE.md: add 'Flow: from the single source of truth to a committed
  change' mermaid diagram (spec/entities.toml + layouts.json -> codegen -> facade
  -> wire -> transport -> executor -> host backend/Scene); fix stale claims
  (hand-maintained enums not 'GENERATED'; accuracy-first mass properties + Scene
  cold-tess budget; with_body borrow; tab auth); add Review round 3 change-log;
  update Known deviations.
- README.md: Core guarantees now include Loft/query caps, accurate mass properties
  (Scene budget persists + graceful fallback), and tab authorization.
- IMPLEMENTATION.md: accuracy paragraph (Scene budget + fallback) + current test
  counts (623 host lib + 8 crate + 3 consistency + 34 plugin_api).
- Regenerate api_reference.md (26 sections) + binding_schema.json (28 ops / 12
  queries / 14 handles / 19 families).
- 623 host lib + 8 crate + 3 consistency + 34 plugin_api green.

crates/ocs_doc_api/README.md

@@ -56,8 +56,16 @@ fn intersect_solids(api: &DocApi) -> ApiResult<()> {
   `brep::combine` is pure; `erase_sources` runs only on success.
 - **Bulk ops** (`CreateMany`/`TransformMany`/`DeleteMany`, and read-only query
   batching) are single ops, **all-or-nothing via upfront validation** (no
-  rollback), item-capped — for bulk data (see `ARCHITECTURE.md` § Performance).
-- **Structured errors** — `ApiError::{Validation, Geometry, UnknownId,
+  rollback), item-capped — for bulk data (see `ARCHITECTURE.md` § Performance).
+  `Loft` and query batches are item-capped the same way (no unbounded kernel call
+  from one request).
+- **Accurate mass properties.** `volume`/`centroid` use a fine tessellation for
+  near-analytic results, memoized per (handle, geometry_epoch) on the per-tab
+  scene; the cold-tessellation budget (256/tab) persists across dispatches and
+  degrades to the coarse mesh value when exhausted.
+- **Tab authorization.** A request must name the tab the session is bound to;
+  mismatched `tab_id` is rejected (no cross-tab access).
+- **Structured errors** — `ApiError::{Validation, Geometry, UnknownId,
   Unsupported, Transport}`, serializable so IPC returns the same error the
   in-process executor produced.