refactor: migrate diff to request-bound runtime
Summary
Migrate the canonical diff descriptor to the request-bound snapshot runtime plan and bind one normalized capture operation after exact fact admission.
Retire the diff capability/legacy admission path and make snapshot/diff share one facts-first binding construction path without capability or capture fallback.
The accepted pre-implementation denominator is recorded on #1739: local Linux/Web capture and eligible provider cells are operation-fact-owned. Capability tests no longer classify diff; unavailable, inactive, or lost owners fail closed before binding.
Split snapshot runtime orchestration into focused command, binding, and diff modules with matching tests; add the parametrized R33 cutover row and plan/fact/provider regressions.
Implementation evidence was gathered against stack/parity base 294654a3a; exact reviewed head f33dc60ca merged as 3f0f706f0. The 23-file change stayed within the diff observation runtime, its shared snapshot construction seam, and owning cutover/layering infrastructure and tests. It did not migrate another command family.
Immediate stack-base deltas: root production TypeScript -2,580 B, workspace package production TypeScript +0 B; raw JS -635 B, gzip JS +10 B, npm tarball -5 B, unpacked -635 B. Changed-scope duplication is 0 groups / 0 lines; daemon→platform remains 62 edges (43 value, 11 type, 8 dynamic).
Validation
pnpm check(915 files, 6,971 tests)pnpm check:affected --run && git push --force-with-lease- changed-line coverage: 81/83 (97.59%); changed branches: 65/70 (92.86%)
- provider-backed diff scenario and all local/provider runtime fact rows
- exact-head GitHub lanes green, including Android, iOS, macOS, Linux, Web, Coverage, Swift compile, Size, Fallow, and Layering