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/constants.ts

@@ -0,0 +1,70 @@
+import color from "picocolors"
+
+export const SYMBOLS = {
+  check: color.green("\u2713"),
+  cross: color.red("\u2717"),
+  warn: color.yellow("\u26A0"),
+  info: color.blue("\u2139"),
+  arrow: color.cyan("\u2192"),
+  bullet: color.dim("\u2022"),
+  skip: color.dim("\u25CB"),
+} as const
+
+export const STATUS_COLORS = {
+  pass: color.green,
+  fail: color.red,
+  warn: color.yellow,
+  skip: color.dim,
+} as const
+
+export const CHECK_IDS = {
+  OPENCODE_INSTALLATION: "opencode-installation",
+  PLUGIN_REGISTRATION: "plugin-registration",
+  CONFIG_VALIDATION: "config-validation",
+  AUTH_ANTHROPIC: "auth-anthropic",
+  AUTH_OPENAI: "auth-openai",
+  AUTH_GOOGLE: "auth-google",
+  DEP_AST_GREP_CLI: "dep-ast-grep-cli",
+  DEP_AST_GREP_NAPI: "dep-ast-grep-napi",
+  DEP_COMMENT_CHECKER: "dep-comment-checker",
+  LSP_SERVERS: "lsp-servers",
+  MCP_BUILTIN: "mcp-builtin",
+  MCP_USER: "mcp-user",
+  VERSION_STATUS: "version-status",
+} as const
+
+export const CHECK_NAMES: Record<string, string> = {
+  [CHECK_IDS.OPENCODE_INSTALLATION]: "OpenCode Installation",
+  [CHECK_IDS.PLUGIN_REGISTRATION]: "Plugin Registration",
+  [CHECK_IDS.CONFIG_VALIDATION]: "Configuration Validity",
+  [CHECK_IDS.AUTH_ANTHROPIC]: "Anthropic (Claude) Auth",
+  [CHECK_IDS.AUTH_OPENAI]: "OpenAI (ChatGPT) Auth",
+  [CHECK_IDS.AUTH_GOOGLE]: "Google (Gemini) Auth",
+  [CHECK_IDS.DEP_AST_GREP_CLI]: "AST-Grep CLI",
+  [CHECK_IDS.DEP_AST_GREP_NAPI]: "AST-Grep NAPI",
+  [CHECK_IDS.DEP_COMMENT_CHECKER]: "Comment Checker",
+  [CHECK_IDS.LSP_SERVERS]: "LSP Servers",
+  [CHECK_IDS.MCP_BUILTIN]: "Built-in MCP Servers",
+  [CHECK_IDS.MCP_USER]: "User MCP Configuration",
+  [CHECK_IDS.VERSION_STATUS]: "Version Status",
+} as const
+
+export const CATEGORY_NAMES: Record<string, string> = {
+  installation: "Installation",
+  configuration: "Configuration",
+  authentication: "Authentication",
+  dependencies: "Dependencies",
+  tools: "Tools & Servers",
+  updates: "Updates",
+} as const
+
+export const EXIT_CODES = {
+  SUCCESS: 0,
+  FAILURE: 1,
+} as const
+
+export const MIN_OPENCODE_VERSION = "1.0.150"
+
+export const PACKAGE_NAME = "oh-my-opencode"
+
+export const OPENCODE_BINARIES = ["opencode", "opencode-desktop"] as const