feat(agent-relay-claude-code): declare and expose the agent_relay_client_platform parameter

[Emyrk]

Description

Declare agent_relay_client_platform, the persistent parameter Agent Relay stamps with the surface that created a Claude Code session (web_claude_ai, claude_in_slack, desktop_app, ...), and expose it to the workspace as AGENT_RELAY_CLIENT_PLATFORM and as the client_platform output so templates can vary their setup by origin.

• Attribution only, not part of the relay's verified contract: a relay that predates the parameter leaves it empty, and a template on the previous module version keeps working with a newer relay (coderd discards the undeclared value).
• Relay side: coder/agent-relay#82.

Type of Change

• Feature/enhancement

Module Information

Path: registry/coder/modules/agent-relay-claude-code
New version: v0.2.0
Breaking change: [ ] Yes [x] No

Testing & Validation

• Tests pass (bun test)
• Code formatted (bun fmt)
• Changes tested locally (terraform test: 8 passed)

Related Issues

RELAY-30

---

_{Coder Agents on behalf of @Emyrk.}

[linear-code]

RELAY-30

[matifali]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-25T13:02:56.499982Z	8daef65	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

Reviewed commit: 8daef65875

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