benilla's own interface loads as one layer after the stock FrameXML and before the addons; the core loads StatsFrame.xml and runs LocaleProperties.lua once, as FrameXML.toc does (#562)

benilla's own interface now loads as one layer on top of the stock UI, as `docs/METHOD.md` now states: the core loads the stock FrameXML rows, the layer (`assets/ui/layer.toc`) loads after the last of them and before the third-party addons, and like FrameXML it has no AddOn API row and fires no `ADDON_LOADED` (the reference loads `FrameXML.toc` outside `AddOn_Load`, `UI_Init` `0x48fbf0`).

- Moved into the layer unchanged: `ScrollTemplates.xml`, `KeyBindingsPage.xml`, `OptionsFrame.xml`, `ContainerFrameAdapters.xml`, `SpellBookAdapters.xml`, `ScriptLogFrame.xml`. `GameMenuFrame.xml` stays the core's last row until #553.
- The host's Lua fixes to stock code (`FCF_ChatTabFadeFinished`, the `DurabilityFrame` re-seat) move into the layer's `FrameXMLFixes.xml`; the resize re-seat stays host-side as an engine adaptation.
- The core now loads `StatsFrame.xml` and runs `LocaleProperties.lua` once, from `UIParent.xml`, so its chain rows are exactly the stock `FrameXML.toc` rows but the menu; the order is #555.
- A dev build boots without the layer under `WOW_STOCK_UI=1`; the host's calls into the layer are guarded.

Verified: new tests for the layer's file list, the core list against the stock toc, the load position (a `_G` definition log), absence from the AddOn API and the stock-only boot, each failing with the change undone; a before/after dump of every global, frame, draw order and saved variable differs only by `StatsFrame` and the moved fixes' source; `scripts/gates.sh` and `scripts/smoke.sh` green, and a live logout/re-login under `WOW_STOCK_UI=1` clean. Built on macOS; no platform seam touched.

Part of #552
Fixes #542
Fixes #543

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

scripts/api-coverage.sh

@@ -66,7 +66,7 @@ awk -F'\t' -v ref="$REF" -v show_missing="$show_missing" -v show_beyond="$show_b
       n_ref["engine"] + n_ref["framexml"] + n_ref["lua"]
     printf "  engine    %5d functions, %5d other   <- benilla implements these in Rust\n", \
       n_ref_fn["engine"], n_ref["engine"] - n_ref_fn["engine"]
-    printf "  framexml  %5d functions, %5d other   <- benilla transcribes these into assets/ui\n", \
+    printf "  framexml  %5d functions, %5d other   <- the stock FrameXML defines these\n", \
       n_ref_fn["framexml"], n_ref["framexml"] - n_ref_fn["framexml"]
     printf "  lua       %5d functions, %5d other   <- mlua provides these\n", \
       n_ref_fn["lua"], n_ref["lua"] - n_ref_fn["lua"]