feat(helpers): acting CDP helpers, HelperCapabilities type, ARIA snapshots for CDP and Puppeteer

[DavertMik]

Summary

aiTrace crashed the whole run under Obscura and Lightpanda. This PR makes the CDP helpers first-class acting helpers, adds a typed capabilities contract for all acting helpers, and brings ARIA snapshots to Lightpanda, Obscura and Puppeteer so aiTrace, pageInfo and Decision can use them.

Fixes

• Obscura and Lightpanda added to Container.STANDARD_ACTING_HELPERS. aiTrace, pageInfo, Decision, screenshot, pause, heal, expose and autoDelay now find them.
• aiTrace called a nonexistent output.warn, so Could not load plugin aiTrace aborted container creation. It now prints the message instead.
• CDPBrowser.saveScreenshot / saveElementScreenshot joined output_dir with absolute paths, so aiTrace step screenshots on Obscura were silently lost. They now resolve paths via screenshotOutputFolder, like Playwright.

CodeceptJS.HelperCapabilities

A new type in typings/index.d.ts that helper authors can implement:

interface HelperCapabilities {
  screenshot: boolean | null   // null = detected at runtime
  video: boolean | null
  trace: boolean
  aria: boolean
  layout?: 'real' | 'none' | null
  xpath?: 'native' | 'polyfill' | null
  innerText?: 'native' | 'computed' | null
}

Helper	screenshot	video	trace	aria
Playwright	true	true	true	true
Puppeteer	true	false	true	true (false on Firefox)
WebDriver / Appium	true	false	false	false
CDPBrowser (Obscura, Lightpanda, Kitesurf)	detected	detected	false	true

The screenshot plugin, captureSnapshot (aiTrace, pageInfo) and Decision skip screenshots and ARIA when a helper declares them false. Lightpanda no longer produces dangling screenshot links in traces.

ARIA snapshots

• CDPBrowser.grabAriaSnapshot(locator = '//body') uses Accessibility.getFullAXTree (supported by Lightpanda and Obscura). It scopes to an element via DOM.describeNode → backendDOMNodeId.
• Puppeteer.grabAriaSnapshot(locator = '//body') uses page.accessibility.snapshot({ root }).
• lib/aria.js renders the engine's tree as a nested - role "name" list. Generic wrappers are dropped, and text that repeats its parent's name is skipped. The output is not normalized to Playwright's format, but it stays parseable by compactAriaSnapshot and diffAriaSnapshots.

Testing

• test/unit/aria_test.js: CDP and Puppeteer trees, scoping, and compact/diff round-trip.
• test/helper/webapi.js: #grabAriaSnapshot for every helper that supports it.
• typings/tests/helper.types.ts: valid and invalid HelperCapabilities objects; npm run def and npm run dtslint pass.
• Ran the checkout example on Lightpanda, Obscura and Puppeteer. grabAriaSnapshot() works on all three, and aiTrace writes an ARIA file per step on Lightpanda.

Not in this PR

• video and trace are declared but not read yet; the screencast plugin still duck-types startScreencast.
• Kitesurf is not in STANDARD_ACTING_HELPERS.
• Obscura does not compute names from <label for>, so checkboxes and radios come out unnamed there.

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