Narrow the error-code rule to what it forbids, and name the fence rule instead of quoting it

AGENTS.md

@@ -76,7 +76,8 @@ The error surface is a contract too. `ConvertError` is `{ code, message, path }`
 closed list a consumer may switch exhaustively, the message free text, the path the node's position
 from the document root. Adding, removing or renaming a code is breaking, so a milestone meeting a
 new failure cause reuses a code where one fits; the list is complete at `0.1.0`. A code names the
-cause, never the node — `path` and `message` carry that.
+cause; where one cause recurs across node types, one code covers them all and `path` and `message`
+say which.
 
 ## 9. Release automation
 

src/corpus.test.ts

@@ -72,8 +72,7 @@ for (const directory of emittingDirectories) {
   }
 }
 
-// The rule spec/flavour.md states as "a container's fence is longer than every directive fence line
-// in its body", checked against the emitted bytes: a hand-written fixture cannot be its own witness.
+// spec/flavour.md, Directives: the container fence rule, checked against the emitted bytes.
 function fenceNestingFault(markdown: string): string | undefined {
   const open: number[] = []
   let codeFence: string | undefined

todo.md

@@ -82,6 +82,8 @@ detail is settled at its own milestone.
         attribute canonicalization, a pipe cell's whitespace edges and `\u007c` for a `|` inside a
         quoted attribute value, documents combining nodes rather than isolating one, and a
         paragraph line inside a container body shaped like a closing fence (`:::`, `::: x`).
+        Guard `fenceNestingFault`'s bare-run pop here too — a run shorter than the open fence is a
+        fault, not a close — which today's emitter cannot reach.
         The gate gains the collision property here: no two corpus documents may emit the same
         bytes — one spelling for two documents is a round-trip break no parser can undo, and it is
         provable without one. It also settles the emitter's one known approximation: delimiter
@@ -114,7 +116,9 @@ detail is settled at its own milestone.
       here too (§10), in `corpus/real-payloads/`: an ADF→markdown→ADF check with no expected
       markdown, the payloads supplied by the maintainer.
 - [ ] **5 — Release pipeline, ship `0.1.0`.** Publish-on-version-change (§9), `NPM_TOKEN` secret,
-      the repo made public first (§6). `0.1.0` is the markdown round-trip: both markdown
+      the repo made public first (§6). The `ConvertErrorCode` freeze (§8) is checkable here: every
+      `corpus/unspellable/` document is one of 1d's decisions, so the directory empties as they land
+      and whatever survives is permanent. `0.1.0` is the markdown round-trip: both markdown
       directions, the types, `isAdfDocument`. The build lands here: a build tsconfig emitting JS
       and `.d.ts` to `dist/` (the dev config's `allowImportingTsExtensions` forces `noEmit`, so
       the build config needs `rewriteRelativeImportExtensions`), plus `exports`/`files` in