Close out verification tasks 9.3 and 9.4

- 9.3: BlackMagic reference tests confirmed green (17 passing, 0 failing);
  WhiteMagic is additive and shares no source or build with it.
- 9.4: document the implementation deviations in the comparison doc's
  synthesis section and correct the InProcessReader architecture line
  (RPM-on-self, not direct deref).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

openspec/changes/whitemagic-foundation/tasks.md

@@ -83,5 +83,5 @@
 
 - [x] 9.1 Run full test suite: `dotnet test WhiteMagicTest/WhiteMagicTest.csproj` — all pass (180 pass, 4 integration/interactive skipped)
 - [x] 9.2 Run full build (`dotnet build WhiteMagic.slnx`) — zero errors, zero new warnings in `WhiteMagic`
-- [ ] 9.3 Confirm existing BlackMagic/its tests are unchanged and still green
-- [ ] 9.4 Update `docs/memory-library-comparison.md` "WhiteMagic — synthesis" section with any deviations discovered during implementation
+- [x] 9.3 Confirm existing BlackMagic/its tests are unchanged and still green. WhiteMagic is a separate, git-ignored project under `reference/` sharing no source or build with BlackMagic; `dotnet test reference/Blackmagic/BlackMagic.slnx` = 17 passing, 0 failing (only pre-existing XML-doc warnings).
+- [x] 9.4 Update `docs/memory-library-comparison.md` "WhiteMagic — synthesis" section with any deviations discovered during implementation. Added a "Deviations discovered during implementation" subsection (D1 RPM-on-self, MarshalCache size split, x64 ABI + SSE proof, export forwarders, partial prologue safety, injection bitness, bounds/protection hardening) and corrected the `InProcessReader` line in the architecture diagram.