refactor(packages): extract model-core package

.omo/evidence/task-3-di-interface.txt

@@ -0,0 +1,19 @@
+Task 3 ProviderCache interface evidence
+
+Defined interface:
+
+- `packages/model-core/src/provider-cache.ts`
+  - `readConnectedProvidersCache(): string[] | null`
+  - `findProviderModelMetadata(providerID: string, modelID: string): ModelMetadata | undefined`
+
+Injection points:
+
+- `packages/model-core/src/model-resolution-pipeline.ts`
+  - `resolveModelPipeline(request, providerCache)` uses `providerCache.readConnectedProvidersCache()`.
+- `packages/model-core/src/model-error-classifier.ts`
+  - `selectFallbackProviderWithCache(providers, providerCache, preferredProviderID?)` uses `providerCache.readConnectedProvidersCache()`.
+
+Adapter wiring in OMO:
+
+- `src/shared/model-resolution-pipeline.ts` passes `connectedProvidersCache` into model-core resolver.
+- `src/shared/model-error-classifier.ts` passes `connectedProvidersCache` into model-core provider selection.

.omo/evidence/task-3-no-coupling.txt

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+Task 3 no-coupling evidence
+
+- Extracted model resolution files into `packages/model-core/src` and replaced original `src/shared/*` with per-file shims.
+- `packages/model-core/src/model-resolution-pipeline.ts` now accepts `providerCache: ProviderCache` and no longer imports `src/shared/connected-providers-cache` directly.
+- `packages/model-core/src/model-error-classifier.ts` exposes `selectFallbackProviderWithCache(...)` and supports cache injection.
+- OMO call-sites receive cache injection through shared adapters:
+  - `src/shared/model-resolution-pipeline.ts` injects `src/shared/connected-providers-cache` into model-core.
+  - `src/shared/model-error-classifier.ts` injects `src/shared/connected-providers-cache` into model-core.

.omo/evidence/task-3-tests.txt

@@ -0,0 +1,8 @@
+Task 3 verification evidence
+
+- `bun run typecheck` => exit 0
+- `bun test` => `7312 pass / 1 skip / 2 fail / 7315 total` (matches baseline)
+- `bun run build` => exit 0
+
+Notes:
+- The 2 failures are pre-existing baseline failures in `src/features/opencode-skill-loader/skill-content.test.ts`.