Feature/stream improvements

[Vyacheslav86RUS]

Stream improvements

This PR improves the internal behavior and reliability of the Stream implementation.

Changes

Refactoring

• Simplified stream mode detection using dynamic checks instead of static mode lists
• Improved close() implementation and resource cleanup
• Safer internal state handling ($this->stream = null after closing)

Behavior Improvements

• Automatic rewind when creating a stream from a non-empty string
• More robust size detection using fstat()
• __toString() now safely catches Throwable as recommended by PSR-7

Testing

• Refactored and reorganized StreamTest
• Added additional edge cases
• Improved append mode pointer behaviour tests

Result

• More predictable stream behavior
• Cleaner and safer internal implementation
• Improved test coverage and readability

No breaking changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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