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/index.ts

@@ -3,9 +3,11 @@ import { Command } from "commander"
 import { install } from "./install"
 import { run } from "./run"
 import { getLocalVersion } from "./get-local-version"
+import { doctor } from "./doctor"
 import type { InstallArgs } from "./types"
 import type { RunOptions } from "./run"
 import type { GetLocalVersionOptions } from "./get-local-version/types"
+import type { DoctorOptions } from "./doctor"
 
 const packageJson = await import("../../package.json")
 const VERSION = packageJson.version
@@ -101,6 +103,37 @@ This command shows:
     process.exit(exitCode)
   })
 
+program
+  .command("doctor")
+  .description("Check oh-my-opencode installation health and diagnose issues")
+  .option("--verbose", "Show detailed diagnostic information")
+  .option("--json", "Output results in JSON format")
+  .option("--category <category>", "Run only specific category")
+  .addHelpText("after", `
+Examples:
+  $ bunx oh-my-opencode doctor
+  $ bunx oh-my-opencode doctor --verbose
+  $ bunx oh-my-opencode doctor --json
+  $ bunx oh-my-opencode doctor --category authentication
+
+Categories:
+  installation     Check OpenCode and plugin installation
+  configuration    Validate configuration files
+  authentication   Check auth provider status
+  dependencies     Check external dependencies
+  tools            Check LSP and MCP servers
+  updates          Check for version updates
+`)
+  .action(async (options) => {
+    const doctorOptions: DoctorOptions = {
+      verbose: options.verbose ?? false,
+      json: options.json ?? false,
+      category: options.category,
+    }
+    const exitCode = await doctor(doctorOptions)
+    process.exit(exitCode)
+  })
+
 program
   .command("version")
   .description("Show version information")