Refactor division methods in Unit class and improve reverse functionality

[chaoming0625]

Now, 1/unit is a Quantity, rather a Unit.

Summary by Sourcery

Extract reciprocal logic into a new Unit.reverse() method, refactor the reverse-division operator to use it, and update tests accordingly.

New Features:

• Introduce a public Unit.reverse() method to return the reciprocal unit.

Enhancements:

• Refactor Unit.__rdiv__ to delegate to Unit.__div__ or Quantity and use reverse() instead of inline reciprocal logic.
• Simplify reverse-division by replacing 1/self unit construction with self.reverse().

Tests:

• Update tests to use reverse() for asserting reciprocal units instead of 1 / unit or 1 / quantity.
• Comment out deprecated tests that directly asserted isinstance(1 / unit, Unit).
• Remove redundant complex unit string-representation test cases.

[sourcery-ai]

Reviewer's Guide

This PR refactors the Unit class’s division logic by extracting inversion into a new reverse() method, simplifies rdiv to use reverse(), and updates/removes tests to reference reverse() instead of computing 1/u and drop outdated assertions.

Sequence Diagram for Unit.__rdiv__ with a Scalar Operand

sequenceDiagram
    participant C as Caller
    participant U as unit: Unit
    participant QC as Quantity Class

    C->>U: __rdiv__(scalar_value)
    activate U
    U->>U: reverse()
    activate U
    U-->>U: inverse_unit : Unit
    deactivate U
    U->>QC: new Quantity(scalar_value, inverse_unit)
    activate QC
    QC-->>U: quantity_instance : Quantity
    deactivate QC
    U-->>C: quantity_instance : Quantity
    deactivate U

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Updated Class Diagram for Unit

classDiagram
    class Unit {
        +__rdiv__(other: any) : Unit_or_Quantity
        +reverse() : Unit
    }

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File-Level Changes

Change	Details	Files
Extracted unit inversion logic into a new reverse() method and simplified rdiv	Added Unit.reverse() to compute dim**-1, scale/factor inversion, and standardization Updated rdiv to delegate scalar division and Quantity cases to reverse() Removed legacy branch handling other==1 in rdiv	saiunit/_base.py
Adapted and pruned tests to use reverse() and removed obsolete division cases	Replaced expected 1/u unit assertions with u.reverse() in division tests Commented out deprecated assertions checking 1/meter returns a Unit Removed outdated str/repr test blocks for complex powered and combined units	saiunit/_base_test.py

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[sourcery-ai]

Hey @chaoming0625 - I've reviewed your changes - here's some feedback:

• The new reverse() method largely duplicates the inversion logic from rdiv; consider extracting a single helper to keep the code DRY.
• The commented-out tests for 1/meter and the large removed block in test_str_repr should be either deleted or accompanied by a clear comment explaining why they’re no longer valid.
• If reverse() is intended as a public API you might choose a more descriptive name (e.g. invert()), or otherwise mark it as a private helper to clarify its usage.

Here's what I looked at during the review

• 🟢 General issues: all looks good
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

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[sourcery-ai]

issue (code-quality): Extract code out into method (extract-method)