chore(tooling): typecheck scripts/** with a dedicated tsgo lane (#104348)

* feat(tooling): add tsgo typecheck lane for scripts/**

* fix(scripts): burn down scripts type debt surfaced by the new lane

Typing-only except bugs the lane surfaced: gh-read timeout race,
Discord Headers spread dropping entries, undefined allowedHeadBranches
match, plugin-boundary matchAll crash. Deletes retired config keys from
fixtures/benches (prompt snapshots regenerated, config dump only) and
the orphaned non-runnable sync-moonshot-docs script. Adds full-surface
.d.mts declarations for existing .mjs boundaries.

scripts/dev/tui-pty-test-watch.ts

@@ -324,8 +324,8 @@ async function main(): Promise<void> {
     },
   );
 
-  let childStdout = Buffer.alloc(0);
-  let childStderr = Buffer.alloc(0);
+  let childStdout: Buffer = Buffer.alloc(0);
+  let childStderr: Buffer = Buffer.alloc(0);
   let restored = false;
   let mirrorOffset = 0;
   let mirrorFilterPending = "";