docs(v4.0.0): ruling -- the unit of heat in v4 is the opcode, not the word

Captain Bob, 2026-10-05: v4 = v3 functionally; heat accumulates on the 32
opcodes; the opcode replaces the word as the smallest unit.  Answers D-6 and
the three conflicts of V3-PARITY.md 2.4.  Records what follows (the
per-call-target array goes; pipelining and the hot-words cache are not
retired; decomposition no longer waits) and what is still open.

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

docs/v4.0.0/V3-PARITY.md

@@ -193,6 +193,45 @@ fabric"). v3's code for each is the reference: `rolling_window_of_truth.c`,
 - **K.** Nothing computes K on v4. It is a figure over heat; it waits for A
   and C.
 
+### 2.7 Ruling (Captain Bob, 2026-10-05)
+
+> One more time: v4 = v3 functionally. We will use [heat accumulation] on
+> 32 opcodes rather than words. Before, a word was our smallest unit; now
+> it is the opcode.
+
+This settles section 2.4:
+
+- **A.** Heat is kept per opcode: 32 accumulators in the node. Not in a
+  word's dictionary entry, and not per call target.
+- **B.** The unit is the opcode. Whether a word is called or compiled in
+  line makes no difference to what is counted. `call` is one of the 32 and
+  is counted as itself.
+- **C.** v4 = v3 functionally, so every loop v3 runs before its prompt
+  runs on v4, over opcodes where v3's runs over words.
+
+What follows from it, and is not yet done:
+
+- The per-call-target array (`v4/src/heat.c`, `call[]`, the freeze mask,
+  `v4_heat_on_call`) has no place and is to be removed, with `HEAT-CALL`
+  in `DECOMPOSITION.md` sections 1.4, 5.19, 5.23 and 7. D-6 is answered:
+  per-opcode.
+- Sections 5.21 and 5.22 of `DECOMPOSITION.md` retire pipelining and the
+  hot-words cache. Under C they are not retired.
+- Decomposition no longer waits on this: moving a word from assembler to a
+  colon definition changes which opcodes run, and those are counted
+  wherever the code is.
+
+Still open, for the words v3 keys by word and v4 must key by something:
+
+- **ACL.** Access control is per word, and v3 works a word's TTL out from
+  that word's heat (`ACL-TTL-COMPUTE`). A v4 word has no heat of its own.
+- **Freeze and pin.** v3 freezes or pins a word's heat (`FREEZE-WORD`,
+  `WORD_PINNED`). In v4 what is frozen is an opcode, or nothing.
+- **Hot-words cache.** v3 promotes a hot word so that it is found faster.
+  A v4 opcode is not looked up.
+- **Heartbeat.** What ticks it on a node (v3: the kernel's timer
+  interrupt).
+
 ## 3. Stand-ins in v4, as found 2026-10-05
 
 Each describes itself as one. None has been changed.