Update CI type diff check

Author: camdecoster

package.json

@@ -30,7 +30,7 @@
     "extra-bundles": "node tasks/extra_bundles.mjs",
     "locales": "node tasks/locales.js",
     "schema": "node tasks/schema.mjs",
-    "schema-typegen-diff-check": "npm run schema && git diff --exit-code src/types/generated/",
+    "schema-typegen-diff-check": "npm run schema && git diff --exit-code src/types/generated/ test/plot-schema.json",
     "stats": "node tasks/stats.js",
     "find-strings": "node tasks/find_locale_strings.js",
     "preprocess": "ts-node tasks/preprocess.js",

src/types/CONVERTING_ATTRIBUTES.md

@@ -94,16 +94,18 @@ should be added to the corresponding `Full*` interface instead.
 ### 6. Verify
 
 ```bash
-npm run typecheck         # zero errors
-npm run schema            # schema regenerates clean
-git diff test/plot-schema.json
-                          # the relevant section should be byte-identical
-                          # to before the conversion
+npm run typecheck                      # zero errors
+npm run schema-typegen-diff-check      # regen + check test/plot-schema.json
+                                       # and src/types/generated/ are unchanged
 ```
 
-If the schema diff is non-empty, the attribute object's runtime shape
-changed somewhere — most often a missed `as const` or a typo. Compare
-character-by-character with the original `.js` file.
+The `schema-typegen-diff-check` script regenerates both the runtime schema
+and the generated `.d.ts`, then `git diff --exit-code`s them. A correct
+conversion produces a byte-identical schema; CI fails otherwise. This is
+the conversion's safety net — if either file diffs after the conversion,
+the attribute object's runtime shape changed (most often a missed
+`as const` or a typo). Compare character-by-character with the original
+`.js` file.
 
 ### 7. Commit
 

src/types/GENERATOR.md

@@ -317,7 +317,15 @@ exported-but-not-re-exported types.
 
 ## CI integration
 
-`npm run schema-typegen-diff-check` runs the generator and then verifies the output
-hasn't drifted via `git diff --exit-code`. If the working tree differs,
-exit code 1 — meaning a developer changed the schema but didn't commit
-the regenerated declarations.
+`npm run schema-typegen-diff-check` runs the generator and then verifies that
+both `test/plot-schema.json` and `src/types/generated/` are unchanged via
+`git diff --exit-code`. If either differs, exit code 1 — meaning either a
+developer changed the source schema but didn't commit the regenerated
+artifacts, or an attribute-file conversion silently altered the runtime
+schema and the change wasn't intentionally committed.
+
+This is what makes the JS-to-TS conversion workflow safe: a correct
+conversion produces a byte-identical schema, so the check passes; an
+incorrect conversion (typo in a `values` array, missed default, wrong
+`valType`) changes the schema and CI fails until the developer fixes the
+source or commits a deliberate change.