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/xhci_driver.h

@@ -233,7 +233,7 @@ typedef struct {
     uint32_t            bot_read10_block_size;
     /* WRITE(10) mirror of bot_read10_* above -- kept as separate fields
      * rather than renaming/reusing the read ones, so the already-tested
-     * READ10 path is never touched by this addition (FABRIC-3.md §F.1). */
+     * READ10 path is never touched by this addition (FABRIC-2.md §F.1). */
     uint32_t            bot_write10_lba;
     uint16_t            bot_write10_num_blocks;
     uint32_t            bot_write10_block_size;