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/vm/stadium_blocks.c

@@ -22,7 +22,7 @@
  */
 
 /**
- * stadium_blocks.c - Block patrons on the Stadium (FABRIC-3.md §B/§D,
+ * stadium_blocks.c - Block patrons on the Stadium (FABRIC-2.md §B/§D,
  * MIGRATE punch-list item). See stadium_blocks.h for the design rationale.
  */
 
@@ -190,7 +190,7 @@ static size_t table_probe(int16_t quota_slot, uint32_t lbn, int *out_found) {
 /*
  * block_dispatch_pull - Reservoir pull for block-touch admission, same
  * Q48_ONE / 3 floor stadium_word_dispatch()'s word_dispatch_pull() enforces
- * and for the identical reason (FABRIC.md §25.5/§25.7): block-touch
+ * and for the identical reason (FABRIC-0.md §25.5/§25.7): block-touch
  * admission alone must never be able to drain a VM's reservoir below the
  * floor other reservoir consumers (word execution, application-level
  * pulls) depend on. Own copy, not shared code across files -- same