refactor(docs): merge quality-house into qfd §3

quality-house.md mirrored qfd.md's §1/§2 catalogues in a separate file,
which silently drifted (H3 cadence read 20 there vs 64 in qfd). Fold the
House diagram, perception scores, and regen notes into qfd.md §3 with no
section renumbering, so inbound #3/#6/#7 anchors still resolve. Delete
quality-house.md; re-point quality-house-empty.md and the docs index.

docs/quality-house-empty.md

@@ -1,9 +1,9 @@
 # Quality House — empty (training)
 
-Same 14 WHATs × 14 HOWs chassis as [`quality-house.md`](quality-house.md),
-with the **relations**, **roof correlations**, and basement Σ / Rel %
-**deliberately blank**. Fill them in yourself, then compare against the
-populated house to check your reading.
+Same 14 WHATs × 14 HOWs chassis as the filled House in
+[`qfd.md` §3](qfd.md#3-house-of-quality--whats--hows), with the **relations**,
+**roof correlations**, and basement Σ / Rel % **deliberately blank**. Fill them
+in yourself, then compare against the populated house to check your reading.
 
 Kept (definitional inputs from `qfd.md`):
 
@@ -368,9 +368,10 @@ Blank (training surface):
 4. **Basement Rel %.** Each Σ ÷ total Σ × 100, rounded to integer percent
    (should sum to ~100 across HOWs).
 
-Once filled, diff your numbers against [`quality-house.md`](quality-house.md)
-basement and roof to see where your reading agrees or differs — divergences
-are usually the most interesting part.
+Once filled, diff your numbers against the filled House in
+[`qfd.md` §3](qfd.md#3-house-of-quality--whats--hows) (basement and roof) to see
+where your reading agrees or differs — divergences are usually the most
+interesting part.
 
 ## Gotchas