GO2 MCAP/DDS integration as memory2 backend

[leshy]

implements MCAP as memory2 Store, allows for standard memory2 queries

cd dimos/robot/unitree/go2dds
python cli/render.py go2_china_office_indoor.mcap --seconds 100 --out test.rrd

in render.py - world lidar to odom alignment is very bad (single function though) builds full odom list and TS aligns lidar to it - will be changed after mem2 stream alignment is merged #2306

[codecov]

Codecov Report

❌ Patch coverage is 93.29173% with 43 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
dimos/memory2/store/mcap.py	82.55%	8 Missing and 7 partials ⚠️
dimos/robot/unitree/go2dds/cdr.py	92.75%	2 Missing and 3 partials ⚠️
dimos/msgs/geometry_msgs/Transform.py	20.00%	4 Missing ⚠️
dimos/robot/unitree/go2dds/codec.py	90.90%	4 Missing ⚠️
dimos/robot/unitree/go2dds/ros.py	96.58%	2 Missing and 2 partials ⚠️
dimos/memory2/stream.py	86.36%	3 Missing ⚠️
dimos/robot/unitree/go2dds/msgs/SportModeState.py	90.32%	3 Missing ⚠️
dimos/memory2/cli/app.py	71.42%	2 Missing ⚠️
dimos/msgs/sensor_msgs/Imu.py	33.33%	2 Missing ⚠️
dimos/utils/cli/map.py	0.00%	1 Missing ⚠️

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[greptile-apps]

Greptile Summary

This PR introduces a full MCAP/DDS integration as a memory2 backend, allowing standard memory2 stream queries over Go2 DDS recordings. A generic McapStore / McapObservationStore pair handles read-only MCAP access (codec-injected, lazy-decode), and a Go2-specific Go2McapStore wires the codec set and stream names on top.

• New MCAP store: McapStore reads the MCAP index at init time, exposes each decodable channel as a named stream with lazy payload decode and cheap O(1) counts for unfiltered queries.
• Go2 DDS codec stack: cdr.py (generic CDR/XCDR1 decoder), codec.py (per-topic wire codecs), ros.py (CDR wire structs → dimos messages), and message dataclasses for all standard Go2 topics.
• Render pipelines: cli/render.py composes stream transforms (leg-odom, IMU dead-reckoning, lidar, world-lidar + global voxel map) into a Rerun .rrd file.

Confidence Score: 5/5

The core MCAP store, CDR decoder, codec registry, and stream pipeline all work correctly for well-formed Go2 recordings; robustness gaps only surface on malformed or unclosed MCAP files.

All findings are confined to edge cases that do not occur in normal Go2 recordings. The happy path is sound.

dimos/robot/unitree/go2dds/ros.py (decode_pointcloud2 alignment and field guards) and dimos/memory2/store/mcap.py (silent empty store on missing statistics).

Important Files Changed

Filename	Overview
dimos/memory2/store/mcap.py	New generic MCAP-backed ObservationStore and Store. count() fast-path correctly detects filters (BeforeFilter is in q.filters). Minor robustness gap: silent empty store when MCAP has no statistics.
dimos/robot/unitree/go2dds/cli/render.py	Pipeline compositions for leg-odom, IMU dead-reckoning, lidar, and world-lidar. world_lidar crashes with IndexError when odom has fewer than 2 messages (already noted); camera() correctly guards against None frames from decode_compressed_image.
dimos/robot/unitree/go2dds/ros.py	CDR-to-dimos decoders for all Go2 channels. decode_pointcloud2 missing alignment guard before view(dt); could crash on malformed/truncated data where data.size % point_step != 0.
dimos/robot/unitree/go2dds/cdr.py	Generic little-endian CDR/XCDR1 decoder driven by cdr_fields specs. Cursor slices do not bounds-check, so a truncated buffer yields silently short strings/arrays; struct.unpack_from would raise on primitives.
dimos/robot/unitree/go2dds/codec.py	DDS wire codec registry. CdrStructCodec.decode uses assert for length validation, disabled under python -O.
dimos/robot/unitree/go2dds/store.py	Thin Go2 wrapper over McapStore: supplies codec set, stream name map, and path resolution. Clean and minimal.
dimos/memory2/stream.py	Adds to_time(), from_time(), range_time() windowing helpers and summary() to Stream. All new methods correctly handle None bounds and empty streams.
dimos/memory2/utils/progress.py	New per-observation progress callback. Handles total=0 gracefully.
dimos/robot/unitree/go2dds/extrinsics.py	Hardcoded L1 lidar extrinsics and camera mount. Well-commented with calibration provenance.

Sequence Diagram

sequenceDiagram
    participant CLI as render.py
    participant Store as Go2McapStore
    participant McapStore as McapStore
    participant Backend as Backend
    participant Obs as McapObservationStore
    participant MCAP as MCAP file

    CLI->>Store: Go2McapStore(path)
    Store->>McapStore: super().__init__(codecs, streams)
    McapStore->>MCAP: open + get_summary()
    MCAP-->>McapStore: channels, statistics
    McapStore-->>Store: _available, _stream_topic

    CLI->>Store: store.streams.sportmodestate.to_time(seconds)
    Store->>Backend: stream() returns Backend
    Backend->>Obs: "McapObservationStore(count=N)"
    CLI->>Obs: count() returns N index fast-path
    CLI->>Obs: query(q) returns iter
    Obs->>MCAP: open + iter_messages(topic)
    MCAP-->>Obs: schema, channel, message
    Obs-->>CLI: Observation with lazy _loader
    CLI->>CLI: obs.data triggers CDR decode

    CLI->>CLI: tap map_data throttle accumulate_path drain
    CLI->>CLI: rr.log for each observation

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