Desk feed pin: say which answerer nulls the bytes show, tie CULTLIB_SHA to the README and doc, note Bifrost consumers

Vendor CultLib's revision and retraction answer vectors (string answerer; no vector nulls them).
The doc and test now say two variants are pinned nulled by bytes (Counted, Refused) and all four
by ruling desk-reader-counts-shape. The sha test requires the fixture README and the doc to name
CULTLIB_SHA verbatim. Doc notes Bifrost heimdall/desk-card-repin (f977a43) re-pin and
DeskDocuments.cs JsonRequired answerer_count.

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

crates/huginn-mind/tests/desk_feed_fixtures.rs

@@ -264,6 +264,8 @@ const VENDORED: &[(&str, &str)] = &[
     ("card-raised-at-nil", "b81bb825790ffe03fabe63c3f8a61c36bd50ca268aa6dff67b5bcfad3957e58c"),
     ("card-withheld-deciders", "d13b9b77461cfdf78f943ef56c6aeab852ab6b6f0b355e26c5b361f99c79c7f7"),
     ("answer-counted", "55d69ae3cc7ebbeeae7d501e8641640e115c3fb5aac399ea760588bca343b9e6"),
+    ("answer-revision", "19d7289395ae68cbaf6de1c0a1ef6c843211b2caf9462e1d2268cd0883386315"),
+    ("answer-retraction", "89156f41ec3ea54f5d47bd3318913ff013785f4727916875be97785935cb7735"),
     ("answer-withheld-answerer", "b66b4f921cdd374be04af3de34c59e254a5e542027ae8c57f196a3ea3406e427"),
     ("answer-refused-stale", "3183bc9c483f4a625332cda11ef22a9c8560868a7728b77daa63a1960a3cd3d6"),
     ("entry-open-counted", "b51f499e8dd0465cf5df9d68d8fccbe94dd1339fd3157969693dd0d4ecb2549b"),
@@ -377,6 +379,13 @@ const RECORD_KEYS: [&str; 6] = ["schemaVersion", "fork_id", "options_hash", "cou
 #[test]
 fn the_vendored_cultlib_vectors_are_the_pinned_bytes() {
     assert_eq!(CULTLIB_SHA.len(), 40);
+    let dir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures/desk-feed/cultlib-3a51bbab");
+    let docs = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../../docs/desk-feed-door.md");
+    for path in [dir.join("README.md"), docs] {
+        let text = std::fs::read_to_string(&path).unwrap_or_else(|error| panic!("{}: {error}", path.display()));
+        assert!(text.contains(CULTLIB_SHA), "{} does not name the pinned sha {CULTLIB_SHA}", path.display());
+    }
+    assert!(dir.to_str().unwrap().ends_with(&format!("cultlib-{}", &CULTLIB_SHA[..8])), "the directory is named for the pin");
     for (name, sha) in VENDORED {
         let digest: String = Sha256::digest(vendored(name)).iter().map(|byte| format!("{byte:02x}")).collect();
         assert_eq!(&digest, sha, "{name} is not CultLib {CULTLIB_SHA}'s bytes");
@@ -410,7 +419,9 @@ fn the_cards_are_eighteen_keys_with_raised_at_and_decider_count() {
     assert_eq!(decode(&vendored("card-withheld-deciders")).get("decider_count").int(), 2);
 }
 
-/// `answerer` is a string or nil on every answer; `Value::Nil` only when `named` is false.
+/// `answerer` is a string or nil on every answer; `Value::Nil` only when `named` is false. The bytes
+/// null it on `Counted` and `Refused` only; nullable on all four variants is the ruling
+/// `desk-reader-counts-shape`, and CultLib has no vector with a `Revision` or `Retraction` nulled.
 fn check_answer(answer: &Value, named: bool) {
     assert_eq!(answer.keys().len(), 16);
     assert_eq!(answer.keys()[13], "answerer");
@@ -423,12 +434,14 @@ fn check_answer(answer: &Value, named: bool) {
 
 #[test]
 fn the_answers_keep_sixteen_keys_and_answerer_is_a_string_or_nil() {
-    for (name, named) in [("answer-counted", true), ("answer-refused-stale", true), ("answer-withheld-answerer", false)] {
+    for (name, named) in [("answer-counted", true), ("answer-revision", true), ("answer-retraction", true), ("answer-refused-stale", true), ("answer-withheld-answerer", false)] {
         let bytes = vendored(name);
         assert_eq!(bytes[..3], [0xde, 0x00, 0x10], "{name}: header");
         check_answer(&decode(&bytes), named);
     }
-    assert_eq!(decode(&vendored("answer-refused-stale")).get("outcome").str(), "Refused");
+    for (name, outcome) in [("answer-counted", "Counted"), ("answer-revision", "Revision"), ("answer-retraction", "Retraction"), ("answer-refused-stale", "Refused")] {
+        assert_eq!(decode(&vendored(name)).get("outcome").str(), outcome);
+    }
 }
 
 /// The entry is `83` and its record `86`, `answerer_count` the fifth key. In a decider's view the count

crates/huginn-mind/tests/fixtures/desk-feed/cultlib-3a51bbab/README.md

@@ -13,6 +13,8 @@ from Huginn's encoders: Huginn's own types do not carry these shapes yet (see
 | `card-raised-at-nil` | `card.valid` `raised_at_nil` | `raised_at` nil, key kept |
 | `card-withheld-deciders` | `card.valid` `withheld_deciders` | empty `deciders`, `decider_count` 2 |
 | `answer-counted` | `deskAnswer.valid` `counted` | 16 keys (`DE 00 10`), `answerer` a string |
+| `answer-revision` | `deskAnswer.valid` `revision` | a `Revision`, `answerer` a string (no CultLib vector nulls a Revision) |
+| `answer-retraction` | `deskAnswer.valid` `retraction` | a `Retraction`, `answerer` a string (no CultLib vector nulls a Retraction) |
 | `answer-withheld-answerer` | `deskAnswer.valid` `withheld_answerer` | `answerer` nil |
 | `answer-refused-stale` | `deskAnswer.valid` `refused_stale` | a `Refused` answer, `answerer` a string |
 | `entry-open-counted` | `transport.entry.valid` `open_counted` | decider view: entry `83`, record `86`, `answerer_count` 1 |

docs/desk-feed-door.md

@@ -138,11 +138,19 @@ byte; both values are in the account-id format above. Any other reader is a non-
     the same for both readers. In a non-decider's view every answerer is nil, and the count is then
     between 1 and the number of answers (0 with no answers).
   - **Answer:** `gamecult.desk_answer.v0` keeps its 16 keys (header `DE 00 10`); `answerer` is a
-    string or nil on all four variants (`Counted`, `Revision`, `Retraction`, `Refused`), nil only in a
-    non-decider's view, with the key kept. Stored answers always carry it.
+    string or nil, nil only in a non-decider's view, with the key kept. The bytes pin a nil `answerer`
+    on two variants, `Counted` (`answer-withheld-answerer`) and `Refused` (the withheld entries). That
+    it is nullable on all four variants (`Counted`, `Revision`, `Retraction`, `Refused`) is the ruling
+    `eureka-substrate:ruling:desk-reader-counts-shape`, not a vector: CultLib's `revision` and
+    `retraction` vectors carry a string `answerer` and no CultLib vector has either nulled. Stored
+    answers always carry it.
   - **Entry:** header `83` (`schemaVersion, card, record`). The view is read off `deciders`: a
     non-empty `deciders` names every answerer, an empty one names none.
   - `options_hash` does not change (still five members).
+  - **Consumers:** Bifrost branch `heimdall/desk-card-repin` (`f977a43`) vendors Huginn's desk
+    fixtures from `79d954c` and needs a re-pin after this PR. Bifrost's `DeskDocuments.cs` marks
+    `answerer_count` `JsonRequired`, so its merge must wait for `cut-desk-feed-listing`: today's door
+    does not send the field.
   - Huginn's real types do not carry these shapes yet: `ForkCard` has no `raised_at` or
     `decider_count`, `ForkRecord` no `answerer_count`, `ForkDeskAnswer.answerer` is a non-null
     string, and each type refuses unknown keys. The test