Add root time assertions

[nfisher]

Motivation

• Provide root-package time.Time assertion helpers mirroring the existing hammy matchers so tests can use concise time assertions directly from gunit.
• Support common time checks including equality, ordering, delta tolerance, and inclusive ranges for clearer test code.

Description

• Add time.go with func Time(t T, actual time.Time) *Tim and type Tim struct { t T; actual time.Time } providing assertion methods.
• Implement EqualTo, Before, BeforeOrEqual, After, AfterOrEqual, WithinDuration(expected time.Time, delta time.Duration), and WithinRange(start, end time.Time) in time.go.
• Add time_test.go with unit tests mirroring hammy/time_test.go to cover success and failure cases for each new assertion.

Testing

• Ran go test ./... and the test suite completed successfully.

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Codex Task