feat(claude-local): add Bedrock model selection support

Previously, --model was completely skipped for Bedrock users, so the
model dropdown selection was silently ignored and the CLI always used
its default model.  Selecting Haiku would still run Opus.

- Add listClaudeModels() that returns Bedrock-native model IDs
  (us.anthropic.*) when Bedrock env is detected
- Register listModels on claude_local adapter so the UI dropdown
  shows Bedrock models instead of Anthropic API names
- Allow --model to pass through when the ID is a Bedrock-native
  identifier (us.anthropic.* or ARN)
- Add isBedrockModelId() helper shared by execute.ts and test.ts

Follows up on #2793 which added basic Bedrock auth detection.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/adapters/registry.ts

@@ -4,6 +4,7 @@ import {
   execute as claudeExecute,
   listClaudeSkills,
   syncClaudeSkills,
+  listClaudeModels,
   testEnvironment as claudeTestEnvironment,
   sessionCodec as claudeSessionCodec,
   getQuotaWindows as claudeGetQuotaWindows,
@@ -94,6 +95,7 @@ const claudeLocalAdapter: ServerAdapterModule = {
   sessionCodec: claudeSessionCodec,
   sessionManagement: getAdapterSessionManagement("claude_local") ?? undefined,
   models: claudeModels,
+  listModels: listClaudeModels,
   supportsLocalAgentJwt: true,
   agentConfigurationDoc: claudeAgentConfigurationDoc,
   getQuotaWindows: claudeGetQuotaWindows,