Fix Copilot VS Code selected model extraction

[Siddhant-K-code]

Summary

• Add Copilot OTEL agent-traces.db model lookup by chat_session_id
• Resolve VS Code Copilot models in order: transcript/event model, OTEL request model, OTEL response model, then models.json default fallback
• Add temp SQLite regression coverage for selected model precedence

Fixes #1559.

Validation

Run from the repo root on this branch:

task fmt
task lint
task test TEST_FILTER=test_copilot_preset_vscode_model_falls_back_to_selected_model_id

Expected outcomes:

• task fmt exits cleanly with no rustfmt diffs.
• task lint exits cleanly with no clippy/lint failures.
• The targeted Copilot model lookup test passes.
• The regression fixture resolves the selected VS Code Copilot model from the OTEL/models lookup path instead of falling back to unknown.

Broader regression sweep:

task test TEST_FILTER=github_copilot

Expected outcome: GitHub Copilot preset tests pass, including native VS Code hook parsing and selected-model fallback behavior.

Additional whitespace check:

git diff --check origin/main..siddhant/1559-copilot-vscode-selected-model

Expected outcome: no output and exit code 0.

Docs

No docs change needed. The fix changes internal model extraction for existing VS Code Copilot sessions and is covered by targeted tests.

Notes

PR for focused review and CI validation.

[devin-ai-integration]

✅ Devin Review: No Issues Found

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