fix: clarify Python pytest failure messages

[kbuffardi]

Closes #23

Summary

• preserve custom assertion feedback without pytest framing
• retain complete default pytest E-line diagnostics for assertions and exceptions
• add dependency-free Node 16-compatible parser regressions
• count pytest errors alongside failed tests

Testing

• npm test

[Copilot]

Pull request overview

Improves Python pytest result parsing so learners receive more constructive, non-truncated failure feedback (custom assertion messages and full E ... diagnostic lines), aligning with Issue #23’s request for clearer outcome messaging.

Changes:

• Reworked parsePytestOutput to extract per-failure error message blocks (including multiline assertion details) and distinguish failures vs errors for counting.
• Added dependency-free Node regression tests covering custom assertion messages, default assertion diffs, exceptions, multiple failures, collection errors, and mixed failure/error runs.
• Updated npm test to run the new regression suite.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
executor.js	Updates pytest output parsing to preserve detailed assertion/exception diagnostics and count errors alongside failures.
test/executor.test.js	Adds Node-based regression tests for pytest parsing behavior across failure/error scenarios.
package.json	Wires npm test to run the new regression tests.

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