Add Foundation Models availability bridge

[backslash-f]

Summary

• expose Apple Foundation Models APIs to IntelligenceBridge consumers without wrapping sessions
• map SystemLanguageModel.Availability into a stable, Sendable bridge value with explicit unsupported-platform fallback
• document the host-owned prompt/session boundary and cover Apple mapping plus consumer import behavior

Validation

• AgentGuidelines/Scripts/swift_format.sh format-and-lint Package.swift Sources Tests
• AgentGuidelines/Scripts/swift_format.sh lint-strict Package.swift Sources Tests
• swift package dump-package
• swift build
• swift test (8 tests)
• swift AgentGuidelines/Scripts/validate_consumer_setup.swift --consumer-root . --require-swift-format
• swift package --scratch-path <isolated> generate-documentation --target IntelligenceBridge
• xcodebuild generic builds: iOS, tvOS, visionOS, Mac Catalyst
• git diff --check

Notes

• The pure availability query intentionally emits no lifecycle logs; it does not perform asynchronous or fallible work.
• tvOS compiles with .unavailable(.unsupportedPlatform) and does not expose unavailable Foundation Models declarations.
• No external dependency was added.

[backslash-f]

Reasoning Relay exact-head review: APPROVED

• Reviewed base: c4202f1d5510ac405beec226d5d60974d65112ff
• Reviewed head: 7d9cf2142cb8e64041dfb7b24cee026cdfda0e68
• Blocking findings: None
• Response hash: 32ebac9fe52b49fe757ae8be42bf04e380622d5534afcf9c33c7058e6a4b845b
• Payload hash: 5154064ea3d26e4d49ebe1836c347550be77723dd9ab344e5ca2cb9c86ac3ac4

Validation remains green for the reviewed head.