refactor(model-core): host snapshot fetcher, suggestion parser, and context-limit resolver

Move three pure helpers from src/shared/ into @oh-my-opencode/model-core so the package can stand alone without depending on plugin internals:

- buildModelCapabilitiesSnapshotFromModelsDev + fetchModelCapabilitiesSnapshot (models.dev normalization)
- parseModelSuggestion (cross-provider ProviderModelNotFoundError suggestion extraction)
- resolveActualContextLimit (Anthropic GA 1M context override)

Split provider-model-id-transform into two variants exposed by model-core:

- transformModelForProvider keeps the runtime dash to dot Anthropic rewrite used by the SDK
- transformModelForProviderDisplay preserves hyphenated Anthropic IDs so the installer writes registry-compatible model strings, fixing the ProviderModelNotFoundError fresh installs hit when the dotted form leaks into the config

src/shared/* and src/cli/provider-model-id-transform.ts collapse to re-export shims that point at the new core modules. Stale src/shared/{known-variants,model-capability-aliases,model-capability-guardrails,model-capability-heuristics}.ts re-export files plus the duplicated context-limit-resolver test are removed in favor of the canonical model-core copies.

Tests: bun test packages/model-core src/shared/model-capabilities-cache.test.ts src/cli/provider-model-id-transform.test.ts

packages/model-core/src/provider-model-id-transform.ts

@@ -24,7 +24,11 @@ function applyGatewayTransforms(model: string): string {
 	)
 }
 
-export function transformModelForProvider(provider: string, model: string): string {
+function transformModelForProviderUsingAnthropicBehavior(
+	provider: string,
+	model: string,
+	directAnthropicTransform: (model: string) => string,
+): string {
 	if (provider === "vercel") {
 		const slashIndex = model.indexOf("/")
 		if (slashIndex !== -1) {
@@ -49,7 +53,26 @@ export function transformModelForProvider(provider: string, model: string): stri
 			.replace(GEMINI_3_FLASH_PREVIEW, "gemini-3-flash-preview")
 	}
 	if (provider === "anthropic") {
-		return claudeVersionDot(model)
+		return directAnthropicTransform(model)
 	}
 	return model
 }
+
+export function transformModelForProvider(provider: string, model: string): string {
+	return transformModelForProviderUsingAnthropicBehavior(
+		provider,
+		model,
+		claudeVersionDot,
+	)
+}
+
+export function transformModelForProviderDisplay(
+	provider: string,
+	model: string,
+): string {
+	return transformModelForProviderUsingAnthropicBehavior(
+		provider,
+		model,
+		(model) => model,
+	)
+}