backend: write robot description to TrossenMCAP files

[abhichothani42]

Summary

Writes the robot's URDF into every MCAP file. On open(), when include_robot_description is set, the backend resolves the URDF through RobotDescriptionCache and logs a single message on a /robot_description channel, so each episode file carries the exact robot model it was recorded with.

Changes

• Add git_ref to the RobotDescription proto so the file records which description version it embeds.
• Add robot_description_topic() (/robot_description) to the TrossenMCAP topic helpers.
• Add the channel setup and single-message write to TrossenMCAPBackend::open(), plus a robot_description_written stat and clean channel teardown in close_resources().

Test Plan

• Builds cleanly (make build)
• Tests pass(make test)
• Lint passes (pre-commit run --all-files)
• Verified on hardware

Breaking Changes

None. With include_robot_description=false (the default) the output files are unchanged.

Related Issues

None.

[abhichothani42]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• scripts: add Foxglove user scripts for robot and EEF visualization #277
• scripts: add URDF extraction tool for TrossenMCAP recordings #276
• examples: enable robot description recording in solo demo #275
• backend: write robot description to TrossenMCAP files #274 👈 (View in Graphite)
• config: add robot description options to TrossenMCAP backend #273
• utils: add RobotDescriptionCache for URDF download and mesh embedding #272
• examples: update sanity check for end-effector pose #270
• arm: emit end-effector pose from TrossenArmProducer #269
• backend: add end-effector pose write support to TrossenMCAP #268
• arm: add EndEffectorPoseRecord and proto schema #267
• examples: add trossen_vr_mobile demo #266
• examples: add trossen_vr_stationary demo #265
• examples: add trossen_vr_solo demo #264
• vr: add VrSessionControlComponent button-to-session bridge #263
• vr: add VrBaseComponent base-velocity teleop leader #262
• vr: add VrArmComponent cartesian teleop leader #261
• vr: add shared VrSession connection owner #260
• feat: post_event/attach_control queue for thread-safe session control #271
• session-control: add SessionControlCapable interface #259
• hw: make SlateBaseComponent a base-velocity teleop follower #258
• teleop: add base-velocity (Base) space to teleop interface #257
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[Copilot]

Pull request overview

This PR enhances the trossen_mcap backend so each recorded MCAP episode can optionally embed the exact robot model (URDF) it was recorded with, improving reproducibility and downstream tooling compatibility.

Changes:

• Add a git_ref field to the RobotDescription protobuf so the embedded URDF can be tied to a specific description version.
• Introduce a fixed /robot_description topic helper for a dedicated robot description channel.
• Write a single RobotDescription message during TrossenMCAPBackend::open() (when enabled), track a robot_description_written stat, and ensure the channel is closed/reset during teardown.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/backends/trossen_mcap/trossen_mcap_backend.cpp	Adds URDF resolution + one-shot write on open; introduces robot description channel creation and teardown; registers the new schema blob.
include/trossen_sdk/io/backends/trossen_mcap/trossen_mcap_schemas.hpp	Adds robot_description_topic() returning /robot_description.
include/trossen_sdk/io/backends/trossen_mcap/trossen_mcap_backend.hpp	Adds stats + members and declares helpers for the robot description channel/message write.
include/trossen_sdk/io/backends/trossen_mcap/proto/RobotDescription.proto	Extends the proto with a git_ref field for provenance.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.