Rename FABRIC series: FABRIC.md->0, FABRIC-2.md->1, FABRIC-3.md->2, FABRIC-4.md unchanged

FABRIC.md -> FABRIC-0.md
FABRIC-2.md -> FABRIC-1.md
FABRIC-3.md -> FABRIC-2.md (the current/living document)
FABRIC-4.md unchanged (new #3 to follow separately)

Every cross-reference repo-wide updated to match, including doc-comment
citations inside kernel source (.c/.h) files -- done via an ordered
placeholder substitution (FABRIC-3.md->placeholder2, FABRIC-2.md->
placeholder1, FABRIC.md->placeholder0, then placeholders resolved to
final names) in a single pass per file to avoid double-shifting
already-renamed references.

One line in capsules/font.4th grew past the 64-char block-format limit
as a side effect of the longer filename; shortened it and reverified
with mkcapsule --lint (34/34 pass) before rebuilding.

Verified 3-arch boot to ok> (amd64/aarch64/riscv64, each in the
foreground) after the fix; logs and DoE CSVs from this session's
verification runs included per this repo's own audit-artifact
convention.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019YcT3H2PQeyujrzjqS3Var

docs/working/architecture/TURTLE-GRAPHICS-HOWTO-20260819.md

@@ -144,7 +144,7 @@ rather than a `POLYGON` call with `n=5`.
     documented in `DOE-LIBRARY-HOWTO-20260819.md`) — it carried a stale
     `TEMP: ... revert once that run is done` comment for a verification
     run that had already closed. Reverted to disabled, matching the
-    file's own note (FABRIC-2.md section K/L).
+    file's own note (FABRIC-1.md section K/L).
   - The kernel's heartbeat CSV logging (`[HADES][DOE ]` rows) draws to
     the *same* console surface `PLOT` draws pixels to, and scrolls
     continuously — anything drawn gets visually overwritten within a