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_runcap.h

@@ -9,7 +9,7 @@
 
 /**
  * capsule_runcap.h - RUNCAP: runtime capsule construction from thumbdrive
- * content (FABRIC-3.md §F.6/§F.18).
+ * content (FABRIC-2.md §F.6/§F.18).
  *
  * A user's identity source (raw FORTH init/personality text, minted by
  * MINT into a home-blocks drive's identity_src region) never exists at
@@ -58,7 +58,7 @@ struct blkio_dev;
  * @param vm_name     Symbolic name for the new VM (becomes both the
  *                    capsule's own single directory entry name and the
  *                    VM registry name).
- * @param parent      Who is birthing this VM (FABRIC-3.md §H.12 step 7) --
+ * @param parent      Who is birthing this VM (FABRIC-2.md §H.12 step 7) --
  *                    passed straight through to capsule_birth_baby().
  * @param out_vm_id   Output: assigned VM ID.
  * @param out_vm_ctx  Output: new VM context (may be NULL if not needed).