refactor(ios): prune converged snapshot paths and close release gates

Parent: #2188

Blocked by: #2195, #2198

## Outcome

Delete the compatibility and backend-name policy that remains solely for the migrated iOS snapshot
implementation, enforce no-regrowth at the owning seams, and run the final package-size,
conformance, provider, Simulator, proxy, and affected release evidence.

This is a deletion and enforcement issue, not a place to finish incomplete behavior from blockers.
Each owning migration must already have removed its obvious local duplication; this issue audits and
closes the cross-cutting remainder.

## Prune audit

Delete when equivalent engine-interface coverage is already proven:

- `shouldPresentIosInteractiveSnapshot` from `src/core/snapshot-state.ts`;
- `backendScopesAfterWire` and remaining backend-name scope planning;
- direct `presentIosInteractiveSnapshot` orchestration from `buildSnapshotState`;
- remaining provider-specific post-wire scope/option branches;
- remaining synthesized WebDriver hittability;
- old iOS semantic-compaction locations after `capture-kit` owns the implementation;
- runner-local Swift geometric-presentation copies after the runner and harness use the shared source;
- simulator observation dependencies on runner readiness and repeated bridge retries after the
generation circuit opens;
- tests whose only purpose was to assert removed producer-name branches, after equivalent behavior is
covered through the engine interface.

Move matching path-keyed fallow baselines rather than regenerating unrelated baselines. Stage new
structural modules before trusting the layering scan.

## Do not delete

- XCTest tree, query-sweep, or private-AX capture backends.
- Apple runner manager/cache, `.xctestrun` preparation, or interaction protocol.
- Swift geometric presentation or TypeScript iOS semantic compaction.
- Generic scope/normalization, refs, quality, occlusion, Android policy, provider acquisition
adapters, golden fixtures, fuzz harnesses, live smokes, or physical-device code.
- Proxy routes, device leases, authentication, artifact transfer, or RPC compatibility machinery.

If deletion appears possible only by weakening another consumer, stop and report the remaining owner
rather than adding a compatibility re-export or fallback.

## No-regrowth enforcement

- Add or update structural ownership tests so producer adapters cannot import presentation behavior,
contracts cannot own algorithms, and root orchestration cannot reconstruct engine policy.
- Reject old path recreation, backend-name scope/presentation branching, or direct iOS presenter
invocation outside the engine.
- Plant each new forbidden direction/path and record the named red failure before returning green.
- Do not add allowlists for unclassified paths; fix the declaration or ownership seam.

## Final evidence

- Compare packed, clean-installed, and bundled npm sizes with #2189. Report exact deltas; do not use
source-line estimates. The compiled bridge cache remains outside the npm artifact.
- Run the independent Swift/TypeScript golden corpus, bounded differential fuzz, properties, and
structural gate with reproducible artifacts.
- Run Appium and Limrun provider contracts on the exact head.
- Run local Simulator cold-cold, cold, warm, relaunch, bridge crash/timeout/cancellation, stale
generation, fallback, and first-runner-interaction evidence.
- Run direct/proxy semantic parity, controlled-RTT performance, lease isolation/expiry, cancellation,
and supported version-skew evidence.
- Run `pnpm check:affected --run`; GitHub remains authoritative for native, provider, coverage, and
full macOS/Simulator lanes.
- Update CLI help/user docs only if observable behavior changed. Do not document internal producer
selection. Keep physical-iPhone behavior explicitly unchanged and separately owned.

## Acceptance

- No compatibility surface remains solely for the migrated implementation.
- Old paths and forbidden dependency directions have observed planted-red no-regrowth proof.
- All child acceptance evidence is linked from #2188 and corresponds to exact implementation heads.
- No open blocker is represented as passing through fixture-only or stale evidence.
- The size delta is within the maintainer-accepted budget and the remote/local performance targets are
met without wrong-tree, stale-tree, lease, or interaction regressions.

## Worker stop conditions

- Stop if #2195 or #2198 is incomplete; do not finish their semantics here.
- Stop if deletion changes another platform/provider/physical-device contract.
- Stop if a baseline would need bulk regeneration or a structural allowlist.
- Do not close #2188 until every child issue and exact-head evidence set is verified.

Vérifiez d’abord que les bloqueurs #2195 et #2198 sont terminés. Lisez ensuite src/core/snapshot-state.ts et le point d’entrée buildSnapshotState, puis les tests de propriété structurelle et les checks concernés. C’est terminé lorsque les chemins obsolètes et les directions de dépendance listés sont supprimés, que les checks planted-red no-regrowth passent et que les éléments probants du release exact-head sont liés sans affaiblir les autres consumers.

Rédigé par le modèle d'indexation à partir du texte de l'issue.