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/repl.h

@@ -74,7 +74,7 @@ VM *sk_repl_get_active_vm(void);
 /**
  * sk_repl_get_homeblocks_dev / sk_repl_get_homeblocks_sig - The currently
  * attached home-blocks USB drive, or NULL if none is attached / the
- * attached drive didn't check out as HOMEBLOCKS_SIG_OK (FABRIC-3.md
+ * attached drive didn't check out as HOMEBLOCKS_SIG_OK (FABRIC-2.md
  * §F.6/§F.9/§F.18). Both return NULL together; never one without the
  * other.
  */
@@ -83,7 +83,7 @@ const homeblocks_sig_t *sk_repl_get_homeblocks_sig(void);
 
 /**
  * sk_repl_get_attached_blk_dev - The currently attached USB block
- * device, regardless of home-blocks recognition (FABRIC-3.md
+ * device, regardless of home-blocks recognition (FABRIC-2.md
  * §F.8/§F.19) -- MINT's own target, since a blank/unminted drive never
  * sets sk_repl_get_homeblocks_dev() above. NULL if nothing is attached.
  */