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

src/starkernel/crypto/ed25519.c

@@ -5,7 +5,7 @@
  *
  * All constants below were generated by direct Python computation
  * (arbitrary-precision arithmetic) and pasted in, not hand-derived or
- * recalled from memory -- see FABRIC-2.md's Ed25519 milestone writeup
+ * recalled from memory -- see FABRIC-1.md's Ed25519 milestone writeup
  * for the derivation. Cross-checked: the curve equation
  * -x^2+y^2 = 1+d*x^2*y^2 holds for (BX,BY) under this D; the base point
  * encoding (0x58, then 0x66 repeating) matches the well-known published