fix(docs): update ADR004 on generated sources

Author: strager

docs/architecture/ADR004-Generated-sources.md

@@ -21,8 +21,14 @@ made.
 Unorthodox artifacts (in addition to unorthodox sources) are checked into the
 source code repository.
 
-The set of unorthodox source files is small. Most changes a typical contributor
-might make do not involve those source files.
+Each unorthodox artifact must include the word 'generated' in its file name.
+
+Each unorthodox artifact must mention in a comment at the top of the file that
+the file is generated, which unorthodox tool generated the file, and what the
+unorthodox sources were.
+
+The set of unorthodox source files is kept small. Most changes a typical
+contributor might make do not involve those source files.
 
 Unorthodox tools are not included in the `vendor` directory (see
 [ADR003](docs/architecture/ADR003-Vendor-sources.md)).
@@ -32,18 +38,18 @@ Unorthodox tools are not included in the `vendor` directory (see
 No unorthodox tools is required in order to build quick-lint-js. Unorthodox
 tools are only required when changing certain source files.
 
-It's sometimes unclear if a file which is checked into the repository is
-generated. This means that a contributor might modify files, but their
-modifications might be destroyed when the unorthodox tool is re-run to re-generate
-those manually-modified files.
+It's clear whether a file which is checked into the repository is generated. A
+contributor might modify an unorthodox artifact, but there are several
+indications that this is a bad idea.
 
 Different versions of unorthodox tools can produce different artifacts given the
 same sources. This can cause thrash it Git logs if two developers trade changes
 to sources but use different different tool versions.
 
 The set of unorthodox sources turned out to be larger than anticipated. For
 example, *all* sources are potentially unorthodox sources for the translation
-tools, and the often-changed `error.h` file is definitely an unorthodox source.
+tools, and the often-changed `diagnostic-types.h` file is definitely an
+unorthodox source.
 
 It's easy for unorthodox artifacts to get out of sync with their unorthodox
 sources. This is clearly true for translation files (.po).