fix(cdp): reject commands for detached sessions

[zyz619963502zyz]

Summary

• track the CDP session associated with each pending command
• reject only that session's pending commands when Target.detachedFromTarget arrives
• keep commands for other live sessions active

Closes #1991

Validation

• regression test fails on the previous implementation because the detached-session command remains pending beyond 1 second
• cargo test detached_session_releases_its_pending_commands -- --nocapture
• cargo test native::cdp::client::tests (12 passed)
• cargo test --bin agent-browser (1394 passed, 142 ignored)
• git diff --check

cargo fmt -- --check could not run because the available pinned Rust toolchain does not include the rustfmt component; no component was installed solely for this change.

AI assistance

AI assistance was used. I reviewed the implementation and verified the behavior and tests above.

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