Fix lint warning and trim AGENTS.md dev-env section

AGENTS.md

@@ -18,12 +18,8 @@ Each userscript is a single `*.user.js` file at the repo root. A script owns eve
 pnpm lint         # lint every *.user.js
 ```
 
-Warnings on third-party/imported scripts are acceptable signal, not blockers. Keep your own scripts warning-clean.
+Keep scripts warning-clean.
 
 ## Dev Environment
 
-The Nix flake provides `nodejs` + `pnpm`; its `shellHook` runs `pnpm install` and puts `node_modules/.bin` on `PATH`, so `oxlint` is ready automatically.
-
-```bash
-nix develop       # or: direnv allow  (uses .envrc → `use flake`)
-```
+direnv (`.envrc` → `use flake`) auto-loads the Nix flake, which provides `nodejs` + `pnpm` and runs `pnpm install` via its `shellHook`, so `oxlint` is on `PATH` automatically.

emdash-highlighter.user.js

@@ -16,7 +16,6 @@
 
   const EM_DASH = '\u2014';
   const EMDASH_REGEX = /\u2014/g;
-  const PROCESSED_ATTR = 'data-emdash-processed';
   const POPUP_ID = 'emdash-popup';
 
   // Tags whose text content we should never touch