feat(cli): add @uid and URL shorthands

[OrKoN]

Adds CLI-only shorthands for element uids and URLs. The MCP server, tool schemas, pageId handling, and snapshot output are unchanged.

• @<uid> is accepted for uid params:
  • In a required uid slot, the @ is stripped: click 1 @1_5 is the same as click 1 1_5.
  • An extra @<uid> fills the first optional uid param that is not set yet: take_screenshot 1 @1_5 becomes take_screenshot 1 --uid 1_5.
  • For evaluate_script, extra @<uid> args are appended to the element --args.
  • --uid @1_5 also works.
• URLs passed as an extra positional fill an optional url param: navigate_page 1 https://web.dev becomes navigate_page 1 --url https://web.dev. Only absolute URLs with http, https, file, chrome, chrome-extension, about, or data schemes count; example.com does not.

Implementation: expandShorthandArgs() in src/config/cli-commands.ts rewrites argv before yargs parses it, so yargs config and strict mode are unchanged. It:

• Skips flag values, using arg types to tell booleans and arrays apart.
• Never overrides an explicit flag: take_screenshot 1 --uid 1_4 @1_5 still fails with "Unknown argument".
• Only strips @ in uid slots, so fill 1 @1_5 @handle keeps the value @handle.

Usage lines show the shorthands (e.g. take_screenshot <pageId> ... [@uid], navigate_page <pageId> ... [url]), and docs/cli.md has a new "Shorthands" section.

The agent tip printed on argument errors now asks for exact command names from --help, uses click 1 @1_2 as the correct example, and lists the @<uid> and URL shorthands for optional parameters. Unknown commands are not rerouted or auto-corrected.

The chrome-devtools-cli skill (skills/chrome-devtools-cli/SKILL.md) now uses the shorthands in its workflow, usage notes, and examples (e.g. click 1 @1_4, take_screenshot 1 @1_4, navigate_page 1 "https://example.com"). I ran each changed example through expandShorthandArgs to check it expands to the expected flags.

Manually verified with the built CLI on wikipedia.org: navigate_page 1 <url>, take_screenshot 1 @uid, evaluate_script ... @uid, fill 1 @uid "@devtools", and click 1 @uid.