fix: keep html reporter auto-open outside the test server

[raashish1601]

Fixes #39766.

Summary

• keep the HTML reporter auto-open path enabled when a regular test run happens outside the test server, even if stdin is not a TTY
• mark reporters created for the test server explicitly so HTML auto-open and the follow-up hint stay suppressed only for that path
• add a regression covering PLAYWRIGHT_HTML_OPEN=always under the test runner with non-TTY stdin

Validation

• npm run ttest -- reporter-html.spec.ts -g "should open report outside test server even when stdin is not a tty"
• npm run eslint -- packages/playwright/src/reporters/html.ts packages/playwright/src/reporters/base.ts packages/playwright/src/runner/reporters.ts packages/playwright/src/runner/testRunner.ts tests/playwright-test/reporter-html.spec.ts
• git diff --check

[pavelfeldman]

I don't think we've achieved a plan in the issue thread.