fix: show Anthropic Opus 4.7+ thinking (#26026)

## Summary

- Updates Coder's pinned `github.com/coder/fantasy` fork to include
coder/fantasy#39.
- Exposes Anthropic `thinking_display` as a typed chat model provider
option with `summarized` and `omitted` values.
- Validates configured `thinking_display` values and maps them to
`fantasyanthropic.ProviderOptions.ThinkingDisplay`.
- Regenerates the API/UI option schemas so the admin model config form
gets a generated select field.

## Tests

- `go mod tidy`
- `make gen`
- `go test ./codersdk ./coderd/x/chatd/chatprovider ./coderd -run
'TestChatModelProviderOptions|TestAnthropicThinkingDisplayFromChat|TestProviderOptionsFromChatModelConfig_AnthropicThinkingDisplay|TestMergeMissingProviderOptions_AnthropicThinkingDisplay|TestValidateChatModelProviderOptions_AnthropicThinkingDisplay'`
- `go test ./coderd/x/chatd/... ./codersdk`
- `go test ./coderd -run
'TestValidateChatModelProviderOptions_AnthropicThinkingDisplay'`
- `pnpm --dir site exec -- biome lint --error-on-warnings
src/api/chatModelOptionsGenerated.json src/api/typesGenerated.ts`
- pre-commit hook, including fmt, lint, and slim build

> Mux working on behalf of Mike.

coderd/exp_chats.go

@@ -7469,7 +7469,19 @@ func validateChatModelCallConfig(modelConfig *codersdk.ChatModelCallConfig) erro
 		}
 	}
 
-	return nil
+	return validateChatModelProviderOptions(modelConfig.ProviderOptions)
+}
+
+func validateChatModelProviderOptions(options *codersdk.ChatModelProviderOptions) error {
+	if options == nil || options.Anthropic == nil || options.Anthropic.ThinkingDisplay == nil {
+		return nil
+	}
+
+	if strings.TrimSpace(*options.Anthropic.ThinkingDisplay) == "" ||
+		chatprovider.AnthropicThinkingDisplayFromChat(options.Anthropic.ThinkingDisplay) != nil {
+		return nil
+	}
+	return xerrors.Errorf("provider_options.anthropic.thinking_display must be one of summarized, omitted")
 }
 
 func validateNonNegativeDecimalField(name string, value *decimal.Decimal) error {