Fixes#51. `Runtime.evaluate` and `Runtime.callFunctionOn` previously
ignored the `contextId` / `executionContextId` parameter entirely, so
clients targeting an isolated world (e.g. Playwright's locator path,
which calls `Page.createIsolatedWorld` → contextId 100 → evaluates the
UtilityScript against that id) silently fell through to the default
context, breaking the contract advertised via
Runtime.executionContextCreated.
Track the set of advertised execution context ids on CdpContext
(pre-seeded with 1 and 2 — the default-frame contexts emitted by
Runtime.enable and post-navigation) and extend it from
Page.createIsolatedWorld. Both handlers now reject unknown ids with
`Cannot find context with specified id: <id>` — matching the wording
real Chrome returns — and log accepted ids at debug for observability.
Obscura still routes every JS call against the page's single V8 isolate,
so this PR is spec-compliance scaffolding rather than full multi-world
execution. Follow-up work to physically isolate worlds can build on the
same valid_context_ids registry.
Ben Younes
2ff0f8fe1d