Show fixture dependency chain in error messages

[MatthewMckee4]

Summary

• When a fixture dependency chain fails (e.g., test requires db -> connection -> config, and config fails), the error now shows the full dependency path
• Previously: Fixture config failed here
• Now: Fixture configfailed here (required bydb->connection)

Test plan

• Added integration test test_fixture_dependency_chain_failure with a 3-level fixture chain (test -> db -> connection -> config, where config fails)
• All 641 existing tests pass
• Pre-commit checks pass

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 1 untouched benchmark

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_{Comparing fixture-dependency-chain-errors (217e7ff) with main (446d5a7)}