Fix HEARTBEAT-TICKS@: read heartbeat_ticks() (ISR hardware timer), not

vm->heartbeat.tick_count (FORTH-dispatch counter)

Captain Bob's law is unambiguous: the adaptive heartbeat is the one and
only clock, full stop. The first cut of this word read the wrong
counter under that name -- vm->heartbeat.tick_count is a colon-word-
dispatch counter gated at a fixed cadence (frozen during idle, blind to
per-dispatch CPU cost, see FABRIC-2.md Section Q). The real adaptive
heartbeat is heartbeat_ticks() in src/starkernel/heartbeat.c, driven
directly by the ISR-latched 100Hz hardware timer -- genuinely
time-based, confirmed advancing during idle wall-clock time on all
three architectures (amd64 4039->5510, aarch64 6126->7607, riscv64
2965->4466, each over ~15s idle). Kernel build only (__STARKERNEL__);
hosted build has no ISR timer and keeps the old fallback.

Three-arch QEMU acceptance: POST 1012/0/0 on each, word live-tested.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

capsules/BLOCK_MAP.md

@@ -1,5 +1,5 @@
 # Capsule Block Manifest — Auto-generated
-<!-- Generated by mkcapsule --manifest  2026-08-21T03:22:02Z -->
+<!-- Generated by mkcapsule --manifest  2026-08-21T13:31:45Z -->
 <!-- DO NOT EDIT — re-run mkcapsule --manifest to refresh.  -->
 <!-- Hand-written justifications and immutability notes live  -->
 <!-- in MANIFEST.md alongside this auto-generated index.      -->