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/dependencies.ts

@@ -0,0 +1,163 @@
+import type { CheckResult, CheckDefinition, DependencyInfo } from "../types"
+import { CHECK_IDS, CHECK_NAMES } from "../constants"
+
+async function checkBinaryExists(binary: string): Promise<{ exists: boolean; path: string | null }> {
+  try {
+    const proc = Bun.spawn(["which", binary], { stdout: "pipe", stderr: "pipe" })
+    const output = await new Response(proc.stdout).text()
+    await proc.exited
+    if (proc.exitCode === 0) {
+      return { exists: true, path: output.trim() }
+    }
+  } catch {
+    // intentionally empty - binary not found
+  }
+  return { exists: false, path: null }
+}
+
+async function getBinaryVersion(binary: string): Promise<string | null> {
+  try {
+    const proc = Bun.spawn([binary, "--version"], { stdout: "pipe", stderr: "pipe" })
+    const output = await new Response(proc.stdout).text()
+    await proc.exited
+    if (proc.exitCode === 0) {
+      return output.trim().split("\n")[0]
+    }
+  } catch {
+    // intentionally empty - version unavailable
+  }
+  return null
+}
+
+export async function checkAstGrepCli(): Promise<DependencyInfo> {
+  const binaryCheck = await checkBinaryExists("sg")
+  const altBinaryCheck = !binaryCheck.exists ? await checkBinaryExists("ast-grep") : null
+
+  const binary = binaryCheck.exists ? binaryCheck : altBinaryCheck
+  if (!binary || !binary.exists) {
+    return {
+      name: "AST-Grep CLI",
+      required: false,
+      installed: false,
+      version: null,
+      path: null,
+      installHint: "Install: npm install -g @ast-grep/cli",
+    }
+  }
+
+  const version = await getBinaryVersion(binary.path!)
+
+  return {
+    name: "AST-Grep CLI",
+    required: false,
+    installed: true,
+    version,
+    path: binary.path,
+  }
+}
+
+export function checkAstGrepNapi(): DependencyInfo {
+  try {
+    require.resolve("@ast-grep/napi")
+    return {
+      name: "AST-Grep NAPI",
+      required: false,
+      installed: true,
+      version: null,
+      path: null,
+    }
+  } catch {
+    return {
+      name: "AST-Grep NAPI",
+      required: false,
+      installed: false,
+      version: null,
+      path: null,
+      installHint: "Will use CLI fallback if available",
+    }
+  }
+}
+
+export async function checkCommentChecker(): Promise<DependencyInfo> {
+  const binaryCheck = await checkBinaryExists("comment-checker")
+
+  if (!binaryCheck.exists) {
+    return {
+      name: "Comment Checker",
+      required: false,
+      installed: false,
+      version: null,
+      path: null,
+      installHint: "Hook will be disabled if not available",
+    }
+  }
+
+  const version = await getBinaryVersion("comment-checker")
+
+  return {
+    name: "Comment Checker",
+    required: false,
+    installed: true,
+    version,
+    path: binaryCheck.path,
+  }
+}
+
+function dependencyToCheckResult(dep: DependencyInfo, checkName: string): CheckResult {
+  if (dep.installed) {
+    return {
+      name: checkName,
+      status: "pass",
+      message: dep.version ?? "installed",
+      details: dep.path ? [`Path: ${dep.path}`] : undefined,
+    }
+  }
+
+  return {
+    name: checkName,
+    status: "warn",
+    message: "Not installed (optional)",
+    details: dep.installHint ? [dep.installHint] : undefined,
+  }
+}
+
+export async function checkDependencyAstGrepCli(): Promise<CheckResult> {
+  const info = await checkAstGrepCli()
+  return dependencyToCheckResult(info, CHECK_NAMES[CHECK_IDS.DEP_AST_GREP_CLI])
+}
+
+export async function checkDependencyAstGrepNapi(): Promise<CheckResult> {
+  const info = checkAstGrepNapi()
+  return dependencyToCheckResult(info, CHECK_NAMES[CHECK_IDS.DEP_AST_GREP_NAPI])
+}
+
+export async function checkDependencyCommentChecker(): Promise<CheckResult> {
+  const info = await checkCommentChecker()
+  return dependencyToCheckResult(info, CHECK_NAMES[CHECK_IDS.DEP_COMMENT_CHECKER])
+}
+
+export function getDependencyCheckDefinitions(): CheckDefinition[] {
+  return [
+    {
+      id: CHECK_IDS.DEP_AST_GREP_CLI,
+      name: CHECK_NAMES[CHECK_IDS.DEP_AST_GREP_CLI],
+      category: "dependencies",
+      check: checkDependencyAstGrepCli,
+      critical: false,
+    },
+    {
+      id: CHECK_IDS.DEP_AST_GREP_NAPI,
+      name: CHECK_NAMES[CHECK_IDS.DEP_AST_GREP_NAPI],
+      category: "dependencies",
+      check: checkDependencyAstGrepNapi,
+      critical: false,
+    },
+    {
+      id: CHECK_IDS.DEP_COMMENT_CHECKER,
+      name: CHECK_NAMES[CHECK_IDS.DEP_COMMENT_CHECKER],
+      category: "dependencies",
+      check: checkDependencyCommentChecker,
+      critical: false,
+    },
+  ]
+}