fix: update stale docstring and suppress UserWarning in cost rendering (#198)

[microsasa]

Summary

Fixes two issues from #198 (unresolved review comments from PR #189):

1. Stale docstring in render_cost_view

The docstring claimed the "↳ Since last shutdown" row uses N/A for premium cost, but the code actually renders an estimated value via _estimate_premium_cost. Updated the docstring to match reality.

2. Noisy UserWarning for unknown models

lookup_model_pricing() emits a UserWarning when it encounters an unknown model name. Since _estimate_premium_cost() is called during normal CLI rendering, this warning surfaces on stderr for end users. Fixed by wrapping the lookup_model_pricing call in warnings.catch_warnings() to suppress UserWarning within the rendering path, so unknown models degrade gracefully to the default 1× multiplier.

Tests added

• TestEstimatePremiumCost: unit tests for _estimate_premium_cost including a no-warning assertion for unknown models
• test_active_session_unknown_model_no_warning: integration test verifying render_cost_view emits no warnings with unknown models

Verification

All CI checks pass locally:

• ruff check ✅
• ruff format ✅
• pyright ✅ (0 errors)
• pytest --cov --cov-fail-under=80 ✅ (442 passed, 98% coverage)

Closes #198

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[Copilot]

Pull request overview

This PR addresses two UX/documentation issues in the Copilot usage reporting layer: it updates render_cost_view’s docstring to reflect current behavior and prevents lookup_model_pricing() warnings from leaking into normal CLI rendering when a session references an unknown model.

Changes:

• Suppress UserWarning from lookup_model_pricing() inside _estimate_premium_cost() so unknown models degrade silently to the default 1× multiplier during rendering.
• Update render_cost_view’s docstring to state that the “↳ Since last shutdown” row shows an estimated premium cost (not N/A).
• Add unit/integration tests covering unknown-model behavior and ensuring no warnings are emitted during cost rendering.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/copilot_usage/report.py	Suppresses pricing lookup warnings within _estimate_premium_cost and updates the render_cost_view docstring.
tests/copilot_usage/test_report.py	Adds tests for _estimate_premium_cost and verifies cost view rendering emits no warnings for unknown models.

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[github-actions]

Commit pushed: 63400f8

Generated by Review Responder

[Copilot]

Pull request overview

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

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[github-actions]

Quality Gate: Auto-approved ✅

Low-impact fix with good test coverage:

• Suppresses UserWarning noise from lookup_model_pricing() during CLI rendering using standard warnings.catch_warnings() — correctly scoped, no global side effects
• Fixes two stale docstrings to match actual behavior
• Adds 5 meaningful tests (4 unit + 1 integration) covering the fix

Impact: LOW (localized rendering helper change + documentation + tests)