docs(v4.0.0): the ACL TTL stays adaptive -- a v4 node counts executions per word

Captain Bob, 2026-10-05: a fixed TTL makes no sense; the hotter the word,
the more often it is checked.  The node counts executions per word at the
call hook for ACL-TTL-COMPUTE, as v3, beside the per-opcode heat.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/v4.0.0/V3-PARITY.md

@@ -306,10 +306,27 @@ to pass through the hook, so it has to be called. The six that cannot be
 called (`>R R> R@ I J LEAVE`) are the residue: they can only appear inside
 a definition, and can only be checked when it is compiled.
 
-**And what v3 measures.** v3 works a word's TTL out from that word's heat
-(`heat/4 + 256`). Section 2.7 rules heat per opcode. A word card exactly as
-v3's needs a count per word, which the same hook could take; whether it
-does is not settled.
+**The TTL is adaptive, as v3 (Captain Bob, 2026-10-05):** "A fixed TTL
+would make no sense whatsoever. The hotter the word, the more frequently
+it's checked."
+
+v3's policy, `capsules/ACL.4th` block 4003: a word's TTL is its own heat
+divided by 4, plus 256, capped — the number of executions until its next
+check. A hot word runs through its TTL sooner and so is checked more often
+than a cold one, while each check is paid for by more executions.
+
+So a v4 node counts executions **per word**, at the call hook, for the
+ACL's use, and `ACL-TTL-COMPUTE` reads that count as it does in v3. This is
+a second count beside the per-opcode heat of section 2.7; in v3 the two are
+one field.
+
+**Not yet settled, and not to be assumed:**
+
+- Whether the per-word count decays as v3's word heat does (Loop #3), and
+  whether a word is then a Stadium patron as in v3 or only the 32 opcodes
+  are.
+- How the node tells a dictionary entry from a bare address at the call.
+- `EXECUTE`, which enters a word by a return.
 
 ## 2. Row 3: physics and per-word heat