starkernel: restate VM fleet heat transfer on the virtual tick

Punch list §25 item 2.1 complete.
vm_physics_touch() no longer takes a wall-clock timestamp -- it reads
fleet_heartbeat_tick_count internally, which is execution-paced
(vm_runtime.c:143), not wall-clock. VMPhysics.last_active_ns ->
last_active_tick, VMFleetTouchSample.elapsed_us -> elapsed_ticks, and a
new explicit `touched` flag replaces the old `> 0` sentinel (tick 0 is
a legitimate value a first touch can land on, unlike wall-clock ns).

Verified: three-architecture boot (amd64 x2, aarch64, riscv64), all
reaching ok> with identical dict_hash=0x3d4e1daf289da94f matching the
item-0.10 baseline. No new compiler warnings in the touched files.

Honestly flagged, not fixed: with Tripod pruned to Hera alone (item
0.1), vm_physics_touch()'s fan-out has no other live VM to pull heat
from, so the fleet-heat-sum acceptance criterion is trivially satisfied
rather than genuinely stress-tested -- a real check needs Phase 4's
multi-VM fleet. fleet_transfer_slope_q48's seed (65536/3) was
calibrated for elapsed microseconds and has not been re-fit for elapsed
ticks; left as-is rather than guessed, deferred to item 5.1's DoE work.

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

src/starkernel/capsule/mama_forth_words.c

@@ -579,7 +579,7 @@ static void mama_word_vm_step(VM *vm)
         return;
     }
 
-    vm_physics_touch(entry.vm_id, vm_monotonic_ns(vm));
+    vm_physics_touch(entry.vm_id);
 
     saved_name = console_get_vm_name();
     console_set_vm_name(entry.name);
@@ -655,7 +655,7 @@ static void mama_word_vm_exec(VM *vm)
         return;
     }
 
-    vm_physics_touch(entry.vm_id, vm_monotonic_ns(vm));
+    vm_physics_touch(entry.vm_id);
 
     log_message(LOG_INFO, "VM-EXEC: '%s' -> '%s'", cmd_buf, vm_name);
     saved_name = console_get_vm_name();
@@ -736,7 +736,7 @@ static void mama_word_vm_call(VM *vm)
         vm_push(vm, 0); return;
     }
 
-    vm_physics_touch(entry.vm_id, vm_monotonic_ns(vm));
+    vm_physics_touch(entry.vm_id);
 
     log_message(LOG_DEBUG, "VM-CALL: '%s' -> '%s'", cmd_buf, vm_name);
     saved_name = console_get_vm_name();