docs: Add environment variable override documentation

[nielspeter]

Summary

• Add documentation comment to default model constants
• Clarifies which environment variables override each constant
• Improves code discoverability for users configuring custom models

Test Plan

• No functional changes
• Documentation only
• Code builds successfully

This is a test PR to verify the Claude Code GitHub Actions workflow.

🤖 Generated with Claude Code

[claude]

PR Review: Documentation Enhancement

Overview

This is a clean documentation-only change that adds helpful comments to the default model constants in internal/converter/converter.go:17. The change improves code discoverability without any functional modifications.

Code Quality ✅

• Style: Follows Go documentation conventions with clear, concise comments
• Placement: Comment is properly positioned above the const block
• Formatting: Consistent indentation and bullet-point style matches Go best practices
• Clarity: Explicitly lists all three environment variable overrides, making configuration immediately obvious

Potential Issues ✅

No bugs or issues detected:

• No functional code changes
• Documentation accurately reflects the actual environment variable names used in the codebase
• No breaking changes or API modifications

Performance Considerations ✅

Impact: None. Documentation comments have zero runtime overhead as they're stripped during compilation.

Security Concerns ✅

Impact: None. This change:

• Does not modify security-sensitive code paths
• Does not introduce new attack vectors
• Simply documents existing configuration options

Test Coverage ✅

Appropriateness: No new tests needed since this is documentation-only. The PR description correctly notes:

• No functional changes
• Code builds successfully
• Existing test suite remains valid

Alignment with CLAUDE.md

The change aligns well with project conventions:

• Supports the "Pattern-Based Model Routing" section which describes these exact environment variables
• Improves maintainability by making the override mechanism discoverable at the point of use
• Complements the existing "Configuration System" documentation

Recommendation

LGTM ✅ - Approve and merge.

This is a valuable improvement that will help users understand how to configure custom model mappings without needing to search through documentation or environment files. The documentation is accurate, well-formatted, and enhances code readability.

Optional Suggestion

Consider adding a similar comment to the mapModel() function (around line ~300-400 in the same file) that references these constants and environment variables, since that's where the actual routing logic lives. This would create a bidirectional documentation trail. Not required for this PR though.