feat: support evaluating scripts from local files

[achideal]

Summary

• extend evaluate_script with sourcePath for loading JavaScript from the MCP server filesystem
• add format: function | script while preserving existing function calls, output redirection, and CLI positional syntax
• validate local source paths through MCP roots and cover page, service worker, and CLI execution

Supersedes #1772.
Fixes #1775.

Test plan

• npm run gen
• npm run test tests/tools/script.test.ts tests/e2e/chrome-devtools-commands.test.ts
• npm run test (feature-related tests pass; the local Windows run has unrelated existing failures: symlink creation requires additional OS privileges, one extension-page timeout, and the large full-page screenshot exceeds Chrome's limit)

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[cbi58105-crypto]

Summary: Adds sourcePath + format to evaluate_script allowing loading local files; supports 'function' and 'script' modes; validates exactly one source and disallows args when format='script'. Tests added covering file loading and error cases. Suggestions: clarify how relative sourcePath is resolved (process.cwd vs repo root) and document file: URL handling; consider clearer error messages for unreadable paths; note ESM modules are not supported. I couldn't run tests locally due to environment (PowerShell execution policy / missing tsc).