[codex] Abstract collector processor view

[colonelpanic8]

Summary

• add a read-only ProcessorView trait implemented by ReplayProcessor
• switch collectors, ndarray feature adders, stats calculators, and test collectors to consume &dyn ProcessorView instead of &ReplayProcessor
• replace collector-side direct event-vector field access with view methods and make FrameInput own sampled state instead of carrying a concrete processor pointer

Impact

Collectors now depend on an abstract processor-like interface, which should make it easier to drive the same collector/stat pipeline from another state source such as BakkesMod later. Replay traversal and mutation still stay on ReplayProcessor.

Validation

• cargo check
• cargo test
• pre-commit hook: cargo clippy --all-targets --all-features -- -D warnings

[colonelpanic8]

Closing as superseded: the collector ProcessorView abstraction and shared FrameInput sampling work have already landed on master through later changes, and this draft branch no longer merges cleanly into current master.