COPILOT_MODEL and GH_AW_INFO_MODEL use different defaults in compiled lock files

[deyaaeldeen]

When vars.GH_AW_MODEL_AGENT_COPILOT is not set, the compiled lock file uses two different fallback values for the same variable:

• GH_AW_INFO_MODEL (telemetry/reporting) defaults to 'auto'
• COPILOT_MODEL (actual agent execution) defaults to 'claude-sonnet-4.6'

This means the model recorded in run metadata can disagree with the model actually used by the Copilot CLI.

Example from a compiled lock file (v0.71.1):

# Line ~110 (generate_aw_info step)
GH_AW_INFO_MODEL: ${{ vars.GH_AW_MODEL_AGENT_COPILOT || 'auto' }}

# Line ~805 (agent execution step)
COPILOT_MODEL: ${{ vars.GH_AW_MODEL_AGENT_COPILOT || 'claude-sonnet-4.6' }}

Both should use the same fallback value.

Compiler version: v0.71.1
Repro: Compile any workflow that uses the Copilot CLI engine without setting vars.GH_AW_MODEL_AGENT_COPILOT and inspect the generated lock file.