Assert the fragile seams: patches, pins, dSYMs and binding drift

[sbokatuk]

• BuildXcFrameworks.sh: every pbxproj patch now asserts it either changed something or found the already-patched state, and fails naming the patch that missed - so an upstream project-file reformat breaks the patch step with a clear message instead of the archive step with a cryptic one. DatadogOtelVersion is verified against the cloned tag's Cartfile.resolved, closing the second manually-synced pin.
• Keep the dSYMs: built into libs/dsyms, cached with the frameworks, uploaded as a CI artifact and attached to every GitHub release - the only symbolication data these Catalyst binaries will ever have, previously discarded with the temp directory.
• Enforce the verbatim-copy invariant: SyncBindingsFromiOS.sh records the DatadogNet.iOS commit it copied from (build/ios-bindings-source.txt), and CI's binding-drift job re-runs the sync against exactly that commit and fails on any difference. shims/ stays outside the sync deliberately; the script's header says what must happen if the iOS Flags shim ever ships.
• Sync the binding sources from DatadogNet.iOS@07ce7ed (DDLogger nullability rationale, entry-type doc summaries) and enable the trim/AOT analyzers, matching the iOS repository.
• Pack docs/release-notes into PackageReleaseNotes; fail CI when README versions drift from Directory.Build.props.
• Fix the stale iOS-specific comments in the copied tooling (merge-packages.py, select-xcode, BuildNugets.sh), each now marked as a keep-in-sync copy.
• Document the net8 sunset: dropped in the first release after .NET 8 leaves support on 10 November 2026, in step with DatadogNet.iOS.