feat(mcp): forward noDefaults to connectOverCDP for --cdp-endpoint connections

[geun9716]

Fixes #41661

Summary

--cdp-endpoint connections (used by both @playwright/mcp and @playwright/cli) go through createCDPBrowser() in packages/playwright-core/src/tools/mcp/browserFactory.ts, which calls chromium.connectOverCDP() but never forwards the noDefaults option added in #40185. It also isn't exposed in config.d.ts's browser section, nor as a CLI flag.

This makes it impossible to attach to CDP targets that reject Playwright's default context-management overrides (e.g. Browser.setDownloadBehavior) sent on connect — the same class of problem noDefaults was introduced to solve (#40158), also reported for other non-Chromium CDP targets (#36961, #15370).

This PR exposes noDefaults as a browser.cdpNoDefaults config field / --cdp-no-defaults CLI flag, mirroring the existing cdpEndpoint / cdpHeaders / cdpTimeout options. Since browserFactory.ts is shared, this fixes both @playwright/mcp and @playwright/cli in one change.

Changes

• packages/playwright-core/src/tools/mcp/config.d.ts: add browser.cdpNoDefaults?: boolean field with JSDoc, documenting that it only affects the pre-existing default context (not newContext()/--isolated), per noDefaults's own design.
• packages/playwright-core/src/tools/mcp/config.ts: add cdpNoDefaults to CLIOptions, forward it in configFromCLIOptions(), and read PLAYWRIGHT_MCP_CDP_NO_DEFAULTS in configFromEnv().
• packages/playwright-core/src/tools/mcp/program.ts: register --cdp-no-defaults CLI flag.
• packages/playwright-core/src/tools/mcp/configIni.ts: register browser.cdpNoDefaults as boolean in longhandTypes for INI config support.
• packages/playwright-core/src/tools/mcp/browserFactory.ts: forward noDefaults: config.browser.cdpNoDefaults into the connectOverCDP call in createCDPBrowser.
• tests/mcp/cdp.spec.ts: add a test that connects with --cdp-no-defaults and asserts that clicking a download link does not produce the usual "Downloading file .../Downloaded file ..." events, mirroring the existing should skip default overrides with noDefaults assertion style from tests/library/chromium/connect-over-cdp.spec.ts (no page.on('download') firing implies Browser.setDownloadBehavior was skipped on connect).

Notes

• noDefaults only ever applies to the pre-existing default context (browser.contexts()[0]), never to contexts created via browser.newContext(). So --isolated combined with --cdp-no-defaults will still fail against targets that reject Target.createBrowserContext — that's expected, not a regression, and matches feat(connectOverCDP): add noDefaults option #40185's original design.
• Naming: I went with cdpNoDefaults / --cdp-no-defaults to match the existing cdp* prefix convention used by cdpEndpoint/cdpHeaders/cdpTimeout. Happy to rename to plain noDefaults if maintainers prefer matching the underlying Playwright API name exactly.
• Verified manually against a real non-Chromium CDP target (a WebKit-based embedded remote debugging endpoint) that previously failed immediately with Protocol error (Browser.setDownloadBehavior): Browser context management is not supported. — with this change and --cdp-no-defaults, the connection succeeds and MCP tools work end-to-end (non-isolated mode). Full write-up is linked from [MCP]: Expose noDefaults for --cdp-endpoint connections (also affects @playwright/cli) #41661.

Versions tested locally: @playwright/mcp@0.0.77, @playwright/cli@0.1.15, playwright-core@1.62.0-alpha-2026-06-29 (this PR is against current main, tip-of-tree).

[geun9716]

@microsoft-github-policy-service agree

[pavelfeldman]

We are going with #41676

[geun9716]

Thanks for the quick turnaround! Looks like #41676 already covers this (and more simply — unconditionally passing noDefaults: true for CDP connections rather than adding an opt-in flag). Closing this one in favor of that PR to avoid duplicate work.