finish phase 4: drop @atproto/api dependency, lex-only errors, delete toLex and legacy validators

oxlint-suppressions.json gains a baseline entry for webpack.config.js: the
file was never previously staged/linted (lint script covers src+modules
only), and editing it exposed its pre-existing violations to lint-staged.
All suppressed counts are pre-existing; this change only removes a line.

webpack.config.js

@@ -45,7 +45,7 @@ function patchSourceMapFilter(rules, pathPattern) {
 
 module.exports = async function (env, argv) {
   env.babel = {
-    dangerouslyAddModulePathsToTranspile: ['@bsky.app/expo', '@atproto/api'],
+    dangerouslyAddModulePathsToTranspile: ['@bsky.app/expo'],
   }
   let config = await createExpoWebpackConfigAsync(env, argv)
   /*