feat: Rerun-compatible CLI args for seamless spawn integration

[spomichter]

Summary

Add clap CLI argument parsing to dimos-viewer so it accepts the same flags that rerun_bindings.spawn() passes to the stock rerun binary.

Motivation

Currently the DimOS bridge uses rr.spawn() which finds and launches the rerun binary with specific CLI args (--port, --memory-limit, --expect-data-soon, etc). To seamlessly swap in our custom viewer, it needs to accept these same args.

With this change, the DimOS bridge can do:

import rerun_bindings
rerun_bindings.spawn(executable_name='dimos-viewer', port=9877)

No rerun-sdk fork needed. No manual pre-launch. Same seamless experience as stock Rerun.

Changes

• Added clap dependency to custom_callback/Cargo.toml
• Added Args struct with Rerun-compatible CLI flags:
  • --port (default 9877, vs stock Rerun's 9876)
  • --memory-limit (default 75%)
  • --server-memory-limit (default 1GiB)
  • --hide-welcome-screen
  • --expect-data-soon
• gRPC server now binds to the port from --port arg instead of hardcoded 9877

Testing

• cargo check passes
• --help shows all expected flags
• Verified exact args from rr.spawn(): --port=9877 --memory-limit=75% --server-memory-limit=1GiB --expect-data-soon parse correctly

Integration (DimOS side)

After this merges, the DimOS Rerun bridge (bridge.py) needs a ~3-line change:

# Instead of: rr.spawn(connect=True)
import rerun_bindings
rerun_bindings.spawn(executable_name='dimos-viewer', port=9877)
rr.connect_grpc('rerun+http://127.0.0.1:9877/proxy')