Default to Zenoh transport on macOS and document replay workflow

[bogwi]

Supersedes #1787.

This PR carries forward the Zenoh transport integration from #1787 and wraps it into a merge-ready branch that fixes the remaining macOS Big Office replay gap.

Validation

• manual macOS replay validation:
  • dimos --transport=zenoh --dtop --replay --replay-dir=unitree_go2_bigoffice run unitree-go2 works smoothly
  • after this change, the plain command dimos --dtop --replay --replay-dir=unitree_go2_bigoffice run unitree-go2 also works on macOS by resolving to Zenoh

Notes

• this PR is intended as the wrapped successor to Feat/integrate zenoh #1787, not a separate redesign
• Linux behavior remains unchanged by default: explicit Zenoh still works, and the default transport remains LCM

[greptile-apps]

Greptile Summary

This PR adds a Zenoh pub/sub transport as an alternative to LCM and defaults to it on macOS when eclipse-zenoh is installed, fixing reliability issues with UDP multicast during heavy replay workloads. All three concerns from the previous review round (import-collection safety, silent pubsubs discard, and missing importorskip guard in test_zenohservice) are addressed in the latest commits.

Confidence Score: 5/5

Safe to merge; all previous P0/P1 concerns are resolved and only minor style/test-reliability suggestions remain.

All three blocking issues from the prior review round (import-collection failures, silent pubsubs discard, missing importorskip) are addressed. Remaining findings are P2: a class-variable style nit on _started, a module-level side-effect ordering in zenohservice, and a potential Barrier deadlock in one test. None of these affect production correctness.

No files require special attention for merge readiness.

Important Files Changed

Filename	Overview
dimos/core/global_config.py	Adds transport field with a platform+availability-aware default factory and validate_assignment=True; clean and well-tested.
dimos/core/transport.py	Adds ZENOH_AVAILABLE sentinel and ZenohTransport/pZenohTransport inside a conditional block; RLock-guarded lazy start is correct, _started class-variable style is the only minor concern.
dimos/core/coordination/module_coordinator.py	Transport branching in _get_transport_for and LCM configurator gating in _run_configurators are well-structured; dimos/ topic prefix correctly applied.
dimos/protocol/service/zenohservice.py	Singleton session management via _sessions dict; stop() intentionally does not close the shared session. Module-level zenoh.init_log_from_env_or side-effect is a minor style concern.
dimos/protocol/pubsub/impl/zenohpubsub.py	Clean raw-bytes Zenoh pubsub with encoder mixins; _topic_to_key_expr/_key_expr_to_topic round-trip logic and known limitations are documented.
dimos/visualization/rerun/bridge.py	Adds _default_pubsubs and _resolve_pubsubs to route the bridge to Zenoh+LCM or LCM-only based on transport config; previous concern about silent pubsubs discard is now addressed via model_fields_set inspection.
dimos/core/test_zenoh_transport.py	Comprehensive tests for transport branching, GlobalConfig validation, and ZenohTransport lifecycle; Zenoh-specific suites correctly guarded with skipif.
dimos/protocol/pubsub/impl/test_zenohpubsub.py	Guarded with pytest.importorskip("zenoh"); test_multiple_subscribers uses a Barrier that could deadlock if Zenoh dispatches callbacks on a single thread.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    CLI["CLI --transport=lcm|zenoh"] --> GC["GlobalConfig.transport\n(default: zenoh on macOS+zenoh, else lcm)"]
    GC --> MC["_get_transport_for()"]
    MC -->|transport==lcm| LCM["LCMTransport / pLCMTransport"]
    MC -->|transport==zenoh| ZT["ZenohTransport / pZenohTransport"]
    ZT --> ZPS["ZenohPubSubBase\n(ZenohService session)"]
    ZPS --> ZS["_sessions singleton\n(ZenohService)"]
    GC --> RP["_resolve_pubsubs()\nin RerunBridgeModule.start()"]
    RP -->|transport==lcm| LCM2["[LCM()]"]
    RP -->|transport==zenoh| ZL["[Zenoh(), LCM()]\n(TF still on LCM)"]
    GC --> RC["_run_configurators()\nskips lcm_configurators\nwhen transport==zenoh"]

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_{Reviews (5): Last reviewed commit: "Merge branch 'dev' into feat/integrate-z..." | Re-trigger Greptile}