v2: Network conditions — offline, throttling, injected latency

[loyality7]

Context

Lets a caller test what a slow or dead connection does to the page under automation. Built on the request-interception path that already exists for blocking.

Scope

• Offline mode toggle.
• Bandwidth throttling.
• Injected per-request latency.

Acceptance criteria

• Offline mode makes in-flight and new requests fail as a real offline device would
• Throttling measurably changes load time on the asset-heavy fixture
• Injected latency is observable and bounded (doesn't itself cause the settle engine to misreport)