refactor(doctor): redesign with 3-tier output and consolidated checks

Consolidate 16 separate checks into 5 (system, config, providers, tools, models).
Add 3-tier formatting: default (problems-only), --status (dashboard), --verbose (deep diagnostics).
Read actual loaded plugin version from opencode cache directory.
Check environment variables for provider authentication.

src/cli/doctor/index.ts

@@ -1,11 +1,11 @@
 import type { DoctorOptions } from "./types"
 import { runDoctor } from "./runner"
 
-export async function doctor(options: DoctorOptions = {}): Promise<number> {
+export async function doctor(options: DoctorOptions = { mode: "default" }): Promise<number> {
   const result = await runDoctor(options)
   return result.exitCode
 }
 
 export * from "./types"
 export { runDoctor } from "./runner"
-export { formatJsonOutput } from "./formatter"
+export { formatDoctorOutput, formatJsonOutput } from "./formatter"