feat(cli): add doctor command for installation health checks (#334)

Implements a comprehensive 'doctor' command that diagnoses oh-my-opencode
installation health with a beautiful TUI output.

Checks performed:
- OpenCode installation (version, path, binary)
- Plugin registration in opencode.json
- Configuration file validity (oh-my-opencode.json)
- Auth providers (Anthropic, OpenAI, Google)
- Dependencies (ast-grep CLI/NAPI, comment-checker)
- LSP servers availability
- MCP servers (builtin and user)
- Version status and updates

Features:
- Beautiful TUI with symbols and colors
- --verbose flag for detailed output
- --json flag for machine-readable output
- --category flag for running specific checks
- Exit code 1 on failures for CI integration

Closes #333

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/cli/doctor/checks/config.ts

@@ -0,0 +1,123 @@
+import { existsSync, readFileSync } from "node:fs"
+import { homedir } from "node:os"
+import { join } from "node:path"
+import type { CheckResult, CheckDefinition, ConfigInfo } from "../types"
+import { CHECK_IDS, CHECK_NAMES, PACKAGE_NAME } from "../constants"
+import { parseJsonc, detectConfigFile } from "../../../shared"
+import { OhMyOpenCodeConfigSchema } from "../../../config"
+
+const USER_CONFIG_DIR = join(homedir(), ".config", "opencode")
+const USER_CONFIG_BASE = join(USER_CONFIG_DIR, `${PACKAGE_NAME}`)
+const PROJECT_CONFIG_BASE = join(process.cwd(), ".opencode", PACKAGE_NAME)
+
+function findConfigPath(): { path: string; format: "json" | "jsonc" } | null {
+  const projectDetected = detectConfigFile(PROJECT_CONFIG_BASE)
+  if (projectDetected.format !== "none") {
+    return { path: projectDetected.path, format: projectDetected.format as "json" | "jsonc" }
+  }
+
+  const userDetected = detectConfigFile(USER_CONFIG_BASE)
+  if (userDetected.format !== "none") {
+    return { path: userDetected.path, format: userDetected.format as "json" | "jsonc" }
+  }
+
+  return null
+}
+
+export function validateConfig(configPath: string): { valid: boolean; errors: string[] } {
+  try {
+    const content = readFileSync(configPath, "utf-8")
+    const rawConfig = parseJsonc<Record<string, unknown>>(content)
+    const result = OhMyOpenCodeConfigSchema.safeParse(rawConfig)
+
+    if (!result.success) {
+      const errors = result.error.issues.map(
+        (i) => `${i.path.join(".")}: ${i.message}`
+      )
+      return { valid: false, errors }
+    }
+
+    return { valid: true, errors: [] }
+  } catch (err) {
+    return {
+      valid: false,
+      errors: [err instanceof Error ? err.message : "Failed to parse config"],
+    }
+  }
+}
+
+export function getConfigInfo(): ConfigInfo {
+  const configPath = findConfigPath()
+
+  if (!configPath) {
+    return {
+      exists: false,
+      path: null,
+      format: null,
+      valid: true,
+      errors: [],
+    }
+  }
+
+  if (!existsSync(configPath.path)) {
+    return {
+      exists: false,
+      path: configPath.path,
+      format: configPath.format,
+      valid: true,
+      errors: [],
+    }
+  }
+
+  const validation = validateConfig(configPath.path)
+
+  return {
+    exists: true,
+    path: configPath.path,
+    format: configPath.format,
+    valid: validation.valid,
+    errors: validation.errors,
+  }
+}
+
+export async function checkConfigValidity(): Promise<CheckResult> {
+  const info = getConfigInfo()
+
+  if (!info.exists) {
+    return {
+      name: CHECK_NAMES[CHECK_IDS.CONFIG_VALIDATION],
+      status: "pass",
+      message: "Using default configuration",
+      details: ["No custom config file found (optional)"],
+    }
+  }
+
+  if (!info.valid) {
+    return {
+      name: CHECK_NAMES[CHECK_IDS.CONFIG_VALIDATION],
+      status: "fail",
+      message: "Configuration has validation errors",
+      details: [
+        `Path: ${info.path}`,
+        ...info.errors.map((e) => `Error: ${e}`),
+      ],
+    }
+  }
+
+  return {
+    name: CHECK_NAMES[CHECK_IDS.CONFIG_VALIDATION],
+    status: "pass",
+    message: `Valid ${info.format?.toUpperCase()} config`,
+    details: [`Path: ${info.path}`],
+  }
+}
+
+export function getConfigCheckDefinition(): CheckDefinition {
+  return {
+    id: CHECK_IDS.CONFIG_VALIDATION,
+    name: CHECK_NAMES[CHECK_IDS.CONFIG_VALIDATION],
+    category: "configuration",
+    check: checkConfigValidity,
+    critical: false,
+  }
+}