docs(v4.0.0): ACLs -- the four cards as built; the word card is to change

Records the stack-of-cards model, that the block, message and VM cards
carry over, and Captain Bob's statement of 2026-10-05 that the word card
changes too, with the reason: the opcode level is the division point for
the machines to be built on the fabric.  What it becomes is not settled.

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

docs/v4.0.0/V3-PARITY.md

@@ -223,6 +223,42 @@ became kernel-Hermes. Not this step. Today Artemis the VM is
 (header, free map, allocator, format and resume, Stadium admission for
 allocated blocks, K total, cooling, reap, self-tests).
 
+## 1f. ACLs (discussed 2026-10-05; the word card is to change)
+
+**v3, as built** (`FABRIC-2.md` section H.3): identity carries its ACL as a
+stack of cards with pinholes through them. Four cards, a closed set: VM,
+word, block, message. An action consults only the cards for the dimensions
+it touches.
+
+- Word card: the four fields in each dictionary entry (`acl_ttl`,
+  `acl_allow`, `acl_mode`, `acl_pinned`); per VM, since each VM has its own
+  dictionary. Checked at every word dispatch in the inner loop.
+- Block card: `acl_allow` and `acl_ttl` in each block's metadata; policy in
+  `block-acl.4th`.
+- Message card: the channel-open question kernel-Hermes puts to `ACL.4th`.
+- VM card: the VM-level dimension.
+- Creator ceiling: a child's ACL state is a snapshot of its parent's at
+  birth.
+- Policy is FORTH; the fields and the hot-path check are C.
+- With physics: a word's TTL is computed from its heat
+  (`heat/4 + 256`, capped), and an ACL is the patron whose leaving is
+  `EXPIRE`.
+
+The block, message and VM cards are decided on the kernel's side and carry
+over under sections 1d and 1e. The word card does not: a v4 node has no
+dispatch point at which to check it, and its TTL comes from per-word heat,
+which v4 has not got (section 2.7).
+
+**Captain Bob, 2026-10-05,** asked whether the word card stays per word:
+"I think it would be wise to change that as well, because as we move down
+our little ladder here into the FPGA area, this is going to be where
+pretty much our division point is going to be. We're going to block things
+off and we're going to build little teeny teeny machines everywhere on the
+fabric."
+
+So the word card changes with the unit of heat. What it becomes is not yet
+settled; see the question put the same day.
+
 ## 2. Row 3: physics and per-word heat
 
 ### 2.1 What v3 does