fix: remove dead code in _build_active_summary (#1202)

[microsasa]

Closes #1202

Summary

Removes two instances of dead/misleading code in parser.py where fp.model is referenced in the active-session path, but is invariably None (since it's only set during SESSION_SHUTDOWN processing).

Changes

1. _build_active_summary (line 979)

# Before
model = fp.model or fp.tool_model

# After
model = fp.tool_model

2. _build_session_summary_with_meta (line 1058)

# Before
used_config = fp.model is None and fp.tool_model is None

# After
used_config = fp.tool_model is None

Testing

Added test_active_summary_uses_tool_model_directly_without_fp_model which:

• Builds a session with TOOL_EXECUTION_COMPLETE (setting fp.tool_model) but no SESSION_SHUTDOWN
• Asserts that fp.model is None and fp.all_shutdowns == ()
• Confirms that SessionSummary.model matches the tool model directly

Warning

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Generated by Issue Implementer · ● 12.3M · ◷

[Copilot]

Pull request overview

This PR removes two pieces of dead/misleading model-resolution logic in the session parser by relying on the correct invariant: for sessions without shutdown events, _first_pass.model is never populated, so the active-session path should use tool_model (and then config fallback) exclusively.

Changes:

• Simplified _build_active_summary to use fp.tool_model directly (instead of fp.model or fp.tool_model).
• Simplified _build_session_summary_with_meta’s used_config_fallback calculation to depend only on whether fp.tool_model is present.
• Added a unit test asserting the invariant (fp.model is None when no shutdown exists) and verifying the resulting SessionSummary.model matches the tool model.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/copilot_usage/parser.py	Removes dead references to fp.model in the no-shutdown (active session) summary path.
tests/copilot_usage/test_parser.py	Adds regression coverage ensuring active sessions resolve the model from tool_model without relying on fp.model.