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

disk/README.md

@@ -85,7 +85,7 @@ carrying timestamp noise in git history.
 
 - `artemis-metafence-fresh.img` — 30MB raw image, blank at creation,
   added 2026-08-26 for the top-of-device system-metadata fence
-  (`meta_fence_blocks` in `blk_volume_meta_t`, FABRIC-3.md Phase 8 §C).
+  (`meta_fence_blocks` in `blk_volume_meta_t`, FABRIC-2.md Phase 8 §C).
   Same reasoning as `artemis-reloc-test.img` above: the fence is only
   initialized to `BLK_META_FENCE_INIT` (128) by
   `blk_compute_fresh_geometry()` on a fresh format, so a genuinely blank
@@ -103,7 +103,7 @@ carrying timestamp noise in git history.
   or misreading adjacent fields.
 
 - `zuse.img` — 64MB raw image simulating the physical Zuse superuser
-  thumbdrive for QEMU testing (FABRIC-3.md, Phase 8: `zuse.img` "bleach"
+  thumbdrive for QEMU testing (FABRIC-2.md, Phase 8: `zuse.img` "bleach"
   mechanism, added 2026-08-26). **64MB is only this fixture's size, not a
   constraint on real home-blocks thumbdrives** (Captain Bob, 2026-08-26) —
   the design is not bound to any particular drive size; `homeblocks_sig_t`'s