refactor(scripts): consolidate gate scripts on mdast fences, parseArgs, and globSync

Implements the gate-consolidation Agent Note from the NIH dependency audit:

- Shared markdownFences helper in scripts/markdown.ts (mdast code-node visit);
  doc-typecheck and verify-type-equiv extract fences through it; md-fences.ts
  and the duplicated extractEquivBlocks regex scanner are deleted;
  markdownProseLines derives fenced lines from parsed code-node positions
  instead of a second fence regex.
- publint-all.ts and verify-built-package-invariants.mjs parse argv with
  node:util parseArgs instead of hand-stepped parseOptions copies.
- Five straggler readdirSync walks become globSync: verify-runtime-closure,
  dev-web discoverPluginDirs, verify-package-paths realPackageNames,
  verify-client-domain-graph listSources, publint-all addPath. The
  dirent-diagnostic walks in check-workspace-constraints.ts and clean.ts stay.

Behavior parity verified: pnpm run doc-sync and every rewritten gate produce
byte-identical output before and after on this tree.

Moves the owning Agent Note proposed -> implemented and re-records its pair.

scripts/verify-package-paths.ts

@@ -5,7 +5,7 @@
  * outside the check.
  */
 
-import { existsSync, readdirSync } from 'node:fs'
+import { existsSync, globSync } from 'node:fs'
 import { resolve } from 'node:path'
 import { findReferenceViolations, uniqueRepoFiles, type ReferenceViolation as Violation } from './repo-files.ts'
 
@@ -36,12 +36,8 @@ const isExcluded = (p: string): boolean =>
  */
 function realPackageNames(): Set<string> {
   const names = new Set<string>()
-  const pkgRoot = resolve(root, 'packages')
-  for (const group of readdirSync(pkgRoot, { withFileTypes: true })) {
-    if (!group.isDirectory()) continue
-    for (const pkg of readdirSync(resolve(pkgRoot, group.name), { withFileTypes: true })) {
-      if (pkg.isDirectory()) names.add(pkg.name)
-    }
+  for (const pkg of globSync('packages/*/*', { cwd: root, withFileTypes: true })) {
+    if (pkg.isDirectory()) names.add(pkg.name)
   }
   return names
 }