findElement: the name filter is one union; a literal is one by grammar

A name is a substring or a regex, never both, so the filter says so
instead of carrying two optionals the caller has to null against each
other. Whether `/.../x` is a literal is now decided by JavaScript's flag
alphabet rather than "looks like letters", which stops `/usr/bin` from
being read as a pattern with flags. Comments that narrated callers or
the type name are gone; the literal parser gets its own test in place
of two MCP round-trips.

src/script/skill.zig

@@ -203,7 +203,7 @@ fn note(tool: browser_tools.Tool) []const u8 {
         .screenshot => "`path` is required: writes a PNG of the text layout.",
         .press => "Selector first! `page.press(\"Enter\")` binds \"Enter\" to `selector` and fails — use `page.press(null, \"Enter\")` or `page.press({ key: \"Enter\" })`.",
         .click, .fill, .scroll, .hover, .selectOption, .setChecked => "",
-        .findElement => "`name` is a case-insensitive substring, or a JS regex literal like `/sign (in|up)/i` (case-insensitive even without `i`).",
+        .findElement => "`name` is a case-insensitive substring, or a JS regex literal like `/sign (in|up)/` (also case-insensitive).",
         .search, .markdown, .html, .links, .tree, .nodeDetails, .interactiveElements, .structuredData, .detectForms, .consoleLogs, .getUrl, .getCookies, .getEnv => "",
     };
 }