Implement FromStr for BitMove and SQ

[Copilot]

• Understand codebase: BitMove::stringify() outputs UCI format like "e2e4" or "a7a8q", but there's no way to parse a BitMove back from a string
• Implement FromStr for SQ in pleco/src/core/sq.rs - parse "a1" through "h8" into SQ values
• Implement FromStr for BitMove in pleco/src/core/piece_move.rs - parse UCI move strings like "e2e4" and "a7a8q"
• Add tests for the new FromStr implementations (6 new tests, all passing)
• Run existing tests to ensure no regressions (all 13 tests pass)
• Code review and security checks (no issues found)
• Fix cargo fmt lint failure

Original prompt

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This section details on the original issue you should resolve

<issue_title>BitMove from string</issue_title>
<issue_description>Noticed there is no real way to de serialize a bitmove without using the raw data. Would be nice if we could use the stringified version</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes BitMove from string #157

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[chase-manning]

@copilot linting ci broken

[Copilot]

@copilot linting ci broken

Fixed in 7094b87 — the write! macro calls in the Display impls for SQFromStrError and BitMoveFromStrError needed line-wrapping to satisfy cargo fmt.