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.

site/src/api/chatModelOptionsGenerated.json

@@ -112,6 +112,16 @@
 					"enum": ["low", "medium", "high", "xhigh", "max"],
 					"input_type": "select"
 				},
+				{
+					"json_name": "thinking_display",
+					"go_name": "ThinkingDisplay",
+					"type": "string",
+					"description": "Controls how Anthropic returns thinking content",
+					"label": "Thinking Display",
+					"required": false,
+					"enum": ["summarized", "omitted"],
+					"input_type": "select"
+				},
 				{
 					"json_name": "disable_parallel_tool_use",
 					"go_name": "DisableParallelToolUse",