Harden automatic SKIE runtime diagnostics

[sonmbol]

Summary

• Cache compatible and incompatible SKIE runtime descriptors per model class, avoiding repeated process-wide Objective-C protocol scans.
• Emit debug diagnostics when automatic SKIE is unavailable, when a StateFlow getter is discovered, and when the generated iterator method shapes are incompatible.
• Validate Objective-C argument counts before dynamically invoking SKIE iterator methods.
• Stop retrying an incompatible iterator selector on every getter read.
• Add focused ABI validation tests and automatic-observation setup performance coverage.

Closes #4

Verification

• swift test -Xswiftc -strict-concurrency=complete -Xswiftc -warnings-as-errors — 32 tests passed.
• ./Scripts/check-api.sh passed.
• swift package dump-package passed.
• git diff --check passed.
• DailyPulse generated SKIE framework built with Java 17.
• DailyPulse iOS simulator app built successfully.