fix(pixel-agent-teams): validate role is recognized enum in worker constructor

[Vishaaallll]

Why this matters

In ods/extensions/services/dashboard-api/pixel_agent_teams.py, worker(team_id, index, role) accesses ROLES[role] directly. Passing an invalid or unregistered role name raises a raw KeyError or causes unintended failure during worker initialization.

This surgical fix verifies role in ROLES, raising a standard ValueError(f"unknown role: {role}") for unapproved role designations.

Validation

• Baseline reproduction: verified that worker(..., "unknown") produced an unhandled KeyError on baseline.
• Post-fix behavior: raises ValueError("unknown role: unknown").
• Telemetry: pixel-teams suite: 2 passed. New-test syntax and diff checks pass; new regression wired into Linux CI.

Overlap check

Inspected open/closed PRs. PR #5734 guarded count in roles_for; zero overlap with worker role enum checking.

Risk / AI disclosure

AI-assisted investigation, patch, and regression tests. Defends worker role initialization. Independent review remains a gate.

Follow-up integration evidence

Composed locally with public-beta at 4fa6ad170 without conflicts. CI and unit checks pass.

[Lightheartdevs]

Thanks for this contribution. public-beta was promoted into main on 2026-09-24 and no longer receives changes, so we're closing pull requests that target it. This isn't a judgment on the change itself. If it's still needed, please rebase onto main and open a focused PR. See #7253 for details and the contribution policy.