Preflight bounded Mach-O chained fixups

[lynnswap]

Purpose

Prevent file-backed chained-fixup metadata from terminating the raw helper on valid sparse iOS 27 tables or malformed external ranges.

Fixes #80.

Changes

• Pin the reviewed MachOKit fix at e0e0b30187ae74f2088d932845c8ddac2c79f36c.
• Track SwiftPM mirrors for both current MxIris MachOKit URL spellings so the direct revision and all transitive requirements resolve to one fork checkout.
• Preflight file-backed chained fixups after loading the Mach-O and before Objective-C or Swift metadata readers consume resolver results.
• Verify the exact MachOKit, MachOObjCSection, and MachOSwiftSection dependency cohort plus the tracked mirror contract.

The dependency fix adds bounded file/image table parsing, correct sparse segment semantics, checked page and chain walking, one validated pointer-index owner, and typed preflight failures while preserving existing public query signatures.

Testing

• swift package --force-resolved-versions resolve
• swift package --force-resolved-versions show-dependencies --format flatlist (no MachOKit identity conflict)
• swift test --force-resolved-versions
• scripts/test-release-scripts.sh
• Xcode 27 iOS Simulator compile: PrivateHeaderKitCore, PrivateHeaderKitCoreTests
• Xcode 27 watchOS Simulator compile: PrivateHeaderKitCore, PrivateHeaderKitCoreTests, privateheaderkit-sim-helper
• MachOKit: swift build; 28 DyldChainedFixupsSafetyTests; branch-wide Codex review clean
• PrivateHeaderKit: branch-wide Codex review clean
• iOS 27.0 beta 24A5390f runtime smoke:
  • PosterBoardUI: completed, 6 artifacts
  • PrivateSearchProtocols: completed, 1 artifact
  • UserManagementUI: completed, 3 artifacts
  • zero run warnings, failure summaries, helper signals, or new incident reports
  • SQLite integrity ok; runtime override restored; run-owned Simulator deleted

Screenshots

Not applicable.

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