chore(runtime): register DYN_REQUEST_PLANE in environment_names

[nnshah1]

Summary

DYN_REQUEST_PLANE selects the request-plane transport (tcp | nats) and is read by the runtime (lib/runtime/src/distributed.rs:835) and the Python launch layer (runtime_args.py, frontend_args.py, --request-plane). But on the Rust side it was referenced by a raw string literal and was missing from the central environment_names registry — unlike its sibling DYN_REQUEST_PLANE_CODEC and every other DYN_* variable, which are defined as pub consts and listed in the known-vars set.

This chore closes that gap:

• Add pub const DYN_REQUEST_PLANE to environment_names::request_plane (next to DYN_REQUEST_PLANE_CODEC).
• Include it in the known-vars list.
• Have distributed.rs reference the const instead of the hardcoded string.

No behavior change — same variable name and semantics; this just makes the registry complete and consistent.

Validation

• cargo fmt clean on the touched files.
• Const reference mirrors the existing pattern in lib/runtime/src/pipeline/network.rs (crate::config::environment_names::request_plane::DYN_REQUEST_PLANE_CODEC).
• Full compile via CI.

🤖 Generated with Claude Code

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Summary by CodeRabbit

• Bug Fixes
  • Improved consistency when reading the request-plane configuration from the environment.
  • Preserved existing parsing and default behavior.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 004cd02 and 898ea97.

📒 Files selected for processing (2)

• lib/runtime/src/config/environment_names.rs
• lib/runtime/src/distributed.rs

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Walkthrough

Changes

Request-plane configuration

Layer / File(s)	Summary
Centralize request-plane environment name lib/runtime/src/config/environment_names.rs, lib/runtime/src/distributed.rs	The public request_plane::DYN_REQUEST_PLANE constant defines the environment variable name. RequestPlaneMode::from_env uses the constant, and duplicate-name test coverage includes it.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Merge Risk: ⚪ Minimal · up to 898ea

This is a localized configuration-name cleanup with unchanged runtime behavior; no actionable merge-blocking risk remains after normal checks, with the separate environment writer suitable for follow-up.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the changes and validation, but it omits the required Related Issues section from the repository template.	Add the required Related Issues section and either link the relevant issue or confirm that no related issue exists.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the main change: registering DYN_REQUEST_PLANE in the runtime environment-name registry.

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