docs(scripts): correct 'no ARG_MAX' claim — argv is still execve-bounded

Copilot is right: spawnSync still calls execve and is subject to the OS
argument-length limit. The runner's real wins are avoiding shell pipeline
exit-code masking and shell word-splitting, not removing ARG_MAX. Reworded the
comments in run-lex-codegen.js and package.json accordingly (the limit is ~2 MB
on Linux, far above this few-KB list).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: aspiers

package.json

@@ -42,7 +42,7 @@
     "check": "npm run gen-api && npm run lint && npm run typecheck && npm run build && npm run test",
     "build": "rollup -c && npm run build:types",
     "build:types": "tsc --project tsconfig.build.json",
-    "//permissions": "permission-set lexicons are published as-is but have no TS shape; lex gen-* cannot codegen them. scripts/run-lex-codegen.js runs a lex subcommand over all lexicons EXCEPT permission-sets (excluded by content — the same check generate-exports.js uses). It is a single Node process that spawns lex with the file list as argv and forwards lex's exit code, so a producer failure propagates without `set -o pipefail` (not portable across npm's sh) and there is no ARG_MAX limit.",
+    "//permissions": "permission-set lexicons are published as-is but have no TS shape; lex gen-* cannot codegen them. scripts/run-lex-codegen.js runs a lex subcommand over all lexicons EXCEPT permission-sets (excluded by content — the same check generate-exports.js uses). It is a single Node process that spawns lex with the file list as argv and forwards lex's exit code, so a producer failure propagates without `set -o pipefail` (not portable across npm's sh) and shell word-splitting is avoided. (argv is still bounded by the OS execve arg limit, ~2 MB on Linux — far above this list.)",
     "gen-api": "node ./scripts/run-lex-codegen.js gen-api --yes ./generated && npm run gen-index",
     "gen-md": "node ./scripts/run-lex-codegen.js gen-md --yes ./lexicons.md",
     "gen-schemas-md": "node ./scripts/generate-schemas.js",

scripts/run-lex-codegen.js

@@ -11,14 +11,17 @@
  * `scripts/generate-exports.js` uses — so the two cannot drift as files move.
  *
  * Why a Node runner rather than a shell pipeline:
- *  - `lex … $(node …)` swallows a producer failure (command substitution discards
- *    its exit code) and can hit ARG_MAX.
+ *  - `lex … $(node …)` swallows a producer failure: command substitution
+ *    discards the inner exit code, so lex runs on whatever (partial/empty)
+ *    output it produced and may report success.
  *  - `node … | xargs -0 lex …` needs `set -o pipefail` to propagate a producer
  *    failure, and `pipefail` is NOT portable across the `sh` npm runs scripts
  *    with (rejected by the dash on GitHub's Ubuntu runners).
- *  This runner is a single process with one authoritative exit code, passes the
- *  file list to `lex` as argv (no shell, no ARG_MAX), and forwards lex's exit
- *  code. No shell builtins involved.
+ *  This runner is a single process with one authoritative exit code: it forwards
+ *  lex's exit code (and fails on an empty list or a spawn error). Passing the
+ *  file list as argv also avoids shell word-splitting/quoting pitfalls. (It does
+ *  not lift the OS `execve` argument-length limit — argv is still bounded — but
+ *  that limit is ~2 MB on Linux, far above the few KB this list occupies.)
  *
  * Usage (in package.json):
  *   node ./scripts/run-lex-codegen.js gen-api --yes ./generated
@@ -73,8 +76,10 @@ if (files.length === 0) {
 }
 
 // `shell: false` (the default) — args are passed as argv, so there is no shell
-// word-splitting, no ARG_MAX limit from a command line, and lex's exit code is
-// ours. stdio inherited so `> file` redirection in the npm script still works.
+// word-splitting/quoting to get wrong, and lex's exit code is ours. (argv is
+// still subject to the OS `execve` arg-length limit, but that is ~2 MB on Linux
+// vs. the few KB this list occupies.) stdio inherited so `> file` redirection in
+// the npm script still works.
 const result = spawnSync("lex", [...lexArgs, ...files], { stdio: "inherit" });
 if (result.error) {
   process.stderr.write(