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

include/starkernel/capsule.h

@@ -87,7 +87,7 @@ typedef enum {
 /** Mama init flag (exactly one capsule must have this) */
 #define CAPSULE_FLAG_MAMA_INIT    0x00000040  /* (m) Mama's init */
 
-/** Contributor capsule flag (FABRIC-3.md §I.5, 2026-09-04) -- path-match
+/** Contributor capsule flag (FABRIC-2.md §I.5, 2026-09-04) -- path-match
  * on capsules/contrib/, mirrors FLAG_MAMA_INIT's own exact-match pattern
  * in mkcapsule.c's flags_from_name(). Trust-tier enforcement (QEMU-vs-
  * real-hardware, decided in conversation) is a runtime check in