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/vm_runtime.c

@@ -747,14 +747,14 @@ void vm_tick_inference_engine(VM* vm)
             }
         }
 
-        /* Punch-list item 0.8 / FABRIC.md §26: drive the physical re-arm
+        /* Punch-list item 0.8 / FABRIC-0.md §26: drive the physical re-arm
          * period from this same execution-derived signal, ratio-preserving
          * rescale onto the kernel's 10 ms base rather than the hosted
          * HEARTBEAT_TICK_NS (10 µs) base -- see §26.3 for why the literal
          * value cannot be used on bare-metal hardware. heartbeat.c clamps
          * defensively on the way in, so no clamping is duplicated here.
          *
-         * FABRIC-2.md, Category B "Multi-VM heartbeat ownership", ruled:
+         * FABRIC-1.md, Category B "Multi-VM heartbeat ownership", ruled:
          * there is exactly one physical timer, so exactly one VM may write
          * its period -- never a race between whichever VM's vm_tick() last
          * ran. Hera is the fixed point everywhere else in this design