add -o json to browsers playwright execute

[rgarcia]

Summary

kernel browsers playwright execute lacked the --output/-o flag that other browsers subcommands expose (create, list, get, view, update, process exec, etc.). Add it using the same pattern: -o json prints the raw API response via util.PrintPrettyJSON, anything else returns the existing pterm tabular output, and unknown values error early.

Test plan

• make build — succeeds
• make test — passes
• ./bin/kernel browsers playwright execute --help shows -o, --output
• manual: kernel browsers playwright execute <id> 'return 1' -o json returns valid JSON

---

Note

Low Risk
Low risk CLI change that only affects formatting/flag parsing for browsers playwright execute, with an early validation error for unsupported --output values.

Overview
Adds --output/-o to kernel browsers playwright execute to match other browsers subcommands.

When -o json is provided, the command now prints the raw Execute API response via util.PrintPrettyJSON; otherwise it keeps the existing table/stdout/stderr rendering, and invalid --output values fail fast.

^{Reviewed by Cursor Bugbot for commit d05c65a. Bugbot is set up for automated code reviews on this repo. Configure here.}

[firetiger-agent]

Firetiger deploy monitoring skipped

This PR didn't match the auto-monitor filter configured on your GitHub connection:

Any PR that changes the kernel API. Monitor changes to API endpoints (packages/api/cmd/api/) and Temporal workflows (packages/api/lib/temporal) in the kernel repo

Reason: PR modifies the browsers playwright command CLI, not the kernel API endpoints (packages/api/cmd/api/) or Temporal workflows (packages/api/lib/temporal) specified in the filter.

To monitor this PR anyway, reply with @firetiger monitor this.

[masnwilliams]

lgtm