Report browser-control CDP commands in the control telemetry category

[archandatta]

Stacked on #322 — the base is that branch, so this diff is only the new event.

Summary

• the CDP proxy emits cdp_command under control for the methods that drive the browser: input gestures, navigation, dialog handling, file selection and screenshots
• configuration and the DOM/Runtime traffic a client library issues on the caller's behalf are not reported; Runtime.evaluate and Runtime.callFunctionOn are excluded deliberately, since every locator resolution is one and including them would bury the gestures
• mouseMoved, keyUp and char are dropped, so a click reads as a press and a release rather than three frames
• payload is shape only: method, session_id, event_type, x, y, button, text_length, and key for keys that command the page (Enter, Tab, arrows, modifiers, F-keys, by allowlist). Never typed characters, never the URL — control is captured by default

Why

api_call covers browser control that arrives through the kernel-images API, but a client driving the browser over the CDP proxy — Playwright, Puppeteer, an SDK — produced nothing at all. A session whose agent works over CDP showed cdp_connect, cdp_disconnect, and nothing in between.

Hot path

Every client frame hits the transform, so classification scans for the frame's method name and does a map lookup; only an allowlisted method is unmarshalled, and a large Runtime.callFunctionOn costs the scan rather than a parse. The scan checks every "method" the frame contains and the parsed top-level method is what decides, so a nested "method" inside params can neither spoof a control command nor hide one.

Existing behavior is unchanged: message relaying, cdp_connect/cdp_disconnect and the message_count they report are untouched, and nothing is emitted for the upstream direction.

Testing

• go vet ./... clean; go test -race green across the non-e2e packages
• new: a classification table (control vs configuration vs library bookkeeping vs command results vs upstream events vs nested-method frames vs malformed), a payload-leakage test asserting text, key, URL and file-path frames leak none of those values, and a proxy-level test asserting two client gestures produce two events while the echoed upstream frames produce none
• TestUpstreamManagerDetectsChromiumAndRestart flakes about 1 in 4 runs on this package — reproduced on the unmodified base, it launches real Chromium. The new tests passed 10/10.
• e2e not run — needs Docker

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Note

Medium Risk
Runs on every client CDP frame in the proxy hot path and emits control telemetry that is on by default; redaction mistakes could leak credentials, though tests explicitly guard typed text and URLs.

Overview
Adds cdp_command telemetry (control) for client→browser CDP traffic through the DevTools WebSocket proxy, so Playwright/Puppeteer sessions are visible between connect and disconnect.

The proxy’s message transform calls publishCdpCommand only on client-to-upstream text frames. New cdpcommand logic allowlists browser-control methods (input, navigation, screenshots, etc.), skips noisy phases (mouseMoved, keyUp, char) and library/runtime bookkeeping, and uses a byte scan before JSON parse on the hot path. Event payloads are shape-only (method, coordinates, text_length, allowlisted named_key)—never typed text, URLs, or file paths.

OpenAPI and generated oapi / category_gen register BrowserCdpCommandEvent and map cdp_command to control. Tests cover classification edge cases, secret leakage, and proxy-level emission counts.

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