Implement random.coinFlip() and random.coinFlipAsync()

[Akashrana1001]

Summary

Closes #77

Implements the random.coinFlip() family of functions as described in the issue:

• random.coinFlip(repetitions?) — sync generator yielding 0 or 1 randomly
• random.coinFlipAsync(repetitions?) — async version
• Stream.ofCoinFlip(repetitions?) — fluent stream factory
• AsyncStream.ofCoinFlip(repetitions?) — async stream factory

Implementation notes

• Follows the identical pattern as random.percentage() / random.booleans()
• Iterates infinitely when repetitions is omitted; terminates after exactly repetitions values otherwise
• Throws InvalidArgumentError for negative repetitions, consistent with the rest of the module

Test plan

• Finite sync: yields exactly N values, each 0 or 1
• Infinite sync: can pull N values from an unbounded generator
• Negative sync: throws InvalidArgumentError
• Finite async: same as sync counterpart
• Infinite async: same as sync counterpart
• Negative async: rejects with InvalidArgumentError
• Stream.ofCoinFlip(): correct count + values, works with .limit()
• AsyncStream.ofCoinFlip(): correct count + values, works with .limit()
• Full test suite: 28,373 tests passing, 100% coverage on all source files

🤖 Generated with Claude Code

[Akashrana1001]

Hi @Smoren, the PR is ready for review. Could you approve the workflow run when you get a chance? Happy to make any changes you need.

[Smoren]

Hi @Akashrana1001
Thznk you for your PR! I merged it. The changes will be included in the next release.