Add adapter environment testing infrastructure

Introduce testEnvironment() on ServerAdapterModule with structured
pass/warn/fail diagnostics for all four adapter types (claude_local,
codex_local, process, http). Adds POST test-environment endpoint,
shared types/validators, adapter test implementations, and UI API
client. Includes asset type foundations used by related features.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/shared/src/validators/agent.ts

@@ -79,6 +79,12 @@ export const resetAgentSessionSchema = z.object({
 
 export type ResetAgentSession = z.infer<typeof resetAgentSessionSchema>;
 
+export const testAdapterEnvironmentSchema = z.object({
+  adapterConfig: adapterConfigSchema.optional().default({}),
+});
+
+export type TestAdapterEnvironment = z.infer<typeof testAdapterEnvironmentSchema>;
+
 export const updateAgentPermissionsSchema = z.object({
   canCreateAgents: z.boolean(),
 });