feat: added chai style assertions

[ronnakamoto]

Description

This PR adds Chai-style assertion names for spy matchers, enabling users migrating from Mocha+Chai+Sinon to use familiar assertion syntax without rewriting their tests.

Resolves #8819

Users migrating from Mocha/Chai/Sinon to Vitest currently need to rewrite all their spy assertions from Chai-style (e.g., expect(spy).to.have.been.called()) to Jest-style (e.g., expect(spy).toHaveBeenCalled()). This creates friction during migration and requires significant test refactoring.

This implementation provides Chai-style assertion names that delegate to existing Jest-style implementations, allowing both styles to coexist.

Added the following assertions that delegate to existing Jest-style implementations:

Call Assertions

Chai-style	Delegates to
called()	toHaveBeenCalled()
callCount(n)	toHaveBeenCalledTimes(n)
calledWith(...args)	toHaveBeenCalledWith(...args)
calledOnce()	toHaveBeenCalledOnce()
calledOnceWith(...args)	toHaveBeenCalledExactlyOnceWith(...args)
calledTwice()	toHaveBeenCalledTimes(2)
calledThrice()	toHaveBeenCalledTimes(3)
lastCalledWith(...args)	toHaveBeenLastCalledWith(...args)
nthCalledWith(n, ...args)	toHaveBeenNthCalledWith(n, ...args)

Return Assertions

Chai-style	Delegates to
returned()	toHaveReturned()
returnedWith(value)	toHaveReturnedWith(value)
returnedTimes(n)	toHaveReturnedTimes(n)
lastReturnedWith(value)	toHaveLastReturnedWith(value)
nthReturnedWith(n, value)	toHaveNthReturnedWith(n, value)

Ordering Assertions

Chai-style	Delegates to
calledBefore(spy)	toHaveBeenCalledBefore(spy)
calledAfter(spy)	toHaveBeenCalledAfter(spy)

Tests

• Run the tests with pnpm test:ci.

Documentation

• Updated documentation

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