[nmcc24]

The 3.0.0-beta.3 matcher work. The stubs of Sendable and actor mocks can be called from any task, so they now take only matchers that are safe there.

Changelog

• b23affa Add SendableMatcher and deprecate users' Matchable conformances. SendableMatcher keeps a @Sendable closure. Each matcher function returns one when the values it keeps are Sendable, and a ParameterMatcher otherwise. Matchers that keep nothing (any(), anyInt(), anyString(), isNil(), notNil(), anyClosure(), hasLength), and sameInstance(as:) for any class, always return a SendableMatcher. or, and and not keep the kind, and an ArgumentCaptor of Sendable values captures with one. Matchable and OptionalMatchable become _Matchable and _OptionalMatchable, with _Sendable… refinements, and the old names are deprecated aliases: pass equal(to:) instead of conforming your own types. A property stub's set takes the Sendable kind for a Sendable mock.
• 2df4cb8 Make Sendable mocks' stubs take only Sendable matchers. The generated stubbing proxies of Sendable and actor mocks take _SendableMatchable arguments and wrap each with a key path, which captures no metatype of a generic method. Verification proxies, and every other mock, take either kind. New fixture 31 covers every matcher kind; fixture 32 must fail to compile (a Sendable mock given a non-Sendable value) and is listed as an expected failure. Snapshots re-recorded.
• 0464934 Document matchers for Sendable mocks and the Matchable deprecation. New "Matchers for Sendable mocks" section in Matching.md (including nonisolated Equatable for projects that isolate to the main actor by default), migration notes, curation, and the CHANGELOG's Unreleased section.
• 239dca0 Roadmap: beta.3 matchers, and hiding Matchable in 4.0. The 4.0 item renames the protocols back to Matchable under @_spi(CuckooGenerated) and removes the aliases (a hard break).

Verified

• Linux, Swift 6.2, 6.3 and 6.4: swift test (543 tests, 13 known issues, 0 warnings; 6.2 also with every upcoming feature on) and the fixture matrix with features off, on, and as a new Xcode 26 project.
• macOS, Xcode 27.2 (Swift 6.4.2): swift test (543 tests, 13 known issues, 0 warnings) and the CuckooTests scheme on the iOS simulator.
• scripts/build-docs.sh on Swift 6.3: no warnings.