user-font-demo.4th: prove the override mechanism (item 4.3.6e)

Punch list §25 item 4.3.6e complete. Optional capsule, not wired into
the boot chain, overriding DISPATCH-UPPER's codepoint 65 (G-A) with a
marked alternate glyph while every other letter falls through to
font.4th's originals unchanged.

Corrects §27.6.5: redefining the DISPATCH-* bucket word alone is not
enough, since DISPATCH-GLYPH/DRAW-GLYPH are themselves compiled early
against font.4th's own dispatch words (same early-binding finding as
4.3.6c, one layer up). Verified both ways: the partial override (bucket
word only) left DRAW-GLYPH still drawing the original glyph; redefining
DISPATCH-GLYPH/DRAW-GLYPH too made the override take effect.

Three-arch acceptance boot clean, Stadium conservation unchanged.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

FABRIC.md

@@ -4579,7 +4579,7 @@ document and committing that amendment as its own item.*
   > (`resident_sum=43691 reservoir=21845 sum=65536`): amd64 (`logs/20260809-202736`),
   > aarch64 (`logs/20260809-203103`), riscv64 (`logs/20260809-203156`).
 
-- [ ] **4.3.6e — User font override.** Mechanism resolved 2026-08-09 (§27.6.5): override
+- [x] **4.3.6e — User font override.** Mechanism resolved 2026-08-09 (§27.6.5): override
   replaces a whole `DISPATCH-*` bucket word, not individual glyphs — `CASE`'s early binding
   means redefining a single glyph word (e.g. `G-A`) alone does not change what an
   already-compiled `DISPATCH-UPPER` calls, so the override capsule must redefine the entire
@@ -4587,6 +4587,28 @@ document and committing that amendment as its own item.*
   `DISPATCH-*` bucket word (e.g. `DISPATCH-UPPER`), and after loading it, drawing a codepoint
   from that bucket renders the overridden glyph, not the default — verified live via
   screendump, both before and after the override loads. *Refs:* §27.6.5.
+  > **Done 2026-08-09.** `capsules/user-font-demo.4th`, blocks 4200-4202. Not wired into
+  > `init.4th` — an optional capsule loaded manually via `EXEC`, same as `doe.4th`.
+  >
+  > **§27.6.5 was incomplete, corrected here rather than silently followed.** The resolved
+  > note said the override capsule must redefine the whole `DISPATCH-*` bucket word — true
+  > but insufficient. `DISPATCH-GLYPH` and `DRAW-GLYPH` are themselves compiled early (in
+  > `font.4th`, against `font.4th`'s own `DISPATCH-UPPER`) — the same finding already hit
+  > once while building 4.3.6c's own dispatch wiring, applying again one layer up. Redefining
+  > only `DISPATCH-UPPER` would not have been picked up; `user-font-demo.4th` redefines
+  > `DISPATCH-UPPER` *and* `DISPATCH-GLYPH`/`DRAW-GLYPH` (blocks 4201-4202). Confirmed by
+  > testing the incomplete version first — redefining `DISPATCH-UPPER` alone left `DRAW-GLYPH`
+  > still drawing the original `G-A`, exactly as the early-binding rule predicts.
+  >
+  > Verified live, single boot, one screendump: codepoint 65 drawn via `DRAW-GLYPH` before
+  > `S" user-font-demo.4th" EXEC` renders the plain default `A`; the same call after renders
+  > `G-A-ALT` (the `A` with a diagonal cross through it), side by side in one image. All
+  > other letters (`G-B`..`G-Z`) render unchanged, calling `font.4th`'s originals directly by
+  > name — proving override granularity is per-bucket, not all-or-nothing across buckets.
+  >
+  > Three-architecture acceptance boot clean, Stadium conservation unchanged
+  > (`resident_sum=43691 reservoir=21845 sum=65536`): amd64 (`logs/20260809-203815`),
+  > aarch64 (`logs/20260809-203858`), riscv64 (`logs/20260809-203950`).
 
 - [ ] **4.3.6f — `TEXT` entry point.** `TEXT ( c-addr u x y size color -- )`: decode UTF-8 via
   4.3.6a, dispatch each codepoint through 4.3.6b/`DRAW-GLYPH`, draw via its stroke word, scale