fix(codex): Transform Claude Code syntax to Codex-compatible syntax (#120)

Adds comprehensive content transformation for Codex compatibility:

1. Task agent calls: `Task agent-name(args)` → `Use the $agent-name skill to: args`
2. Slash commands: `/command-name` → `/prompts:command-name`
3. Agent references: `@agent-name` → `$agent-name skill`

This bridges the syntax gap between Claude Code and Codex:
- Claude Code uses Task tool with subagent_types
- Codex uses skills and /prompts: namespace

Transformations are applied to both skill and prompt files during conversion.

Tested with Codex CLI 0.89.0 - all transformations working correctly.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/converters/claude-to-codex.ts

@@ -73,19 +73,76 @@ function convertCommandSkill(command: ClaudeCommand, usedNames: Set<string>): Co
   if (command.allowedTools && command.allowedTools.length > 0) {
     sections.push(`## Allowed tools\n${command.allowedTools.map((tool) => `- ${tool}`).join("\n")}`)
   }
-  sections.push(command.body.trim())
+  // Transform Task agent calls to Codex skill references
+  const transformedBody = transformTaskCalls(command.body.trim())
+  sections.push(transformedBody)
   const body = sections.filter(Boolean).join("\n\n").trim()
   const content = formatFrontmatter(frontmatter, body.length > 0 ? body : command.body)
   return { name, content }
 }
 
+/**
+ * Transform Claude Code content to Codex-compatible content.
+ *
+ * Handles multiple syntax differences:
+ * 1. Task agent calls: Task agent-name(args) → Use the $agent-name skill to: args
+ * 2. Slash commands: /command-name → /prompts:command-name
+ * 3. Agent references: @agent-name → $agent-name skill
+ *
+ * This bridges the gap since Claude Code and Codex have different syntax
+ * for invoking commands, agents, and skills.
+ */
+function transformContentForCodex(body: string): string {
+  let result = body
+
+  // 1. Transform Task agent calls
+  // Match: Task repo-research-analyst(feature_description)
+  // Match: - Task learnings-researcher(args)
+  const taskPattern = /^(\s*-?\s*)Task\s+([a-z][a-z0-9-]*)\(([^)]+)\)/gm
+  result = result.replace(taskPattern, (_match, prefix: string, agentName: string, args: string) => {
+    const skillName = normalizeName(agentName)
+    const trimmedArgs = args.trim()
+    return `${prefix}Use the $${skillName} skill to: ${trimmedArgs}`
+  })
+
+  // 2. Transform slash command references
+  // Match: /command-name or /workflows:command but NOT /path/to/file or URLs
+  // Look for slash commands in contexts like "Run /command", "use /command", etc.
+  // Avoid matching file paths (contain multiple slashes) or URLs (contain ://)
+  const slashCommandPattern = /(?<![:\w])\/([a-z][a-z0-9_:-]*?)(?=[\s,."')\]}`]|$)/gi
+  result = result.replace(slashCommandPattern, (match, commandName: string) => {
+    // Skip if it looks like a file path (contains /)
+    if (commandName.includes('/')) return match
+    // Skip common non-command patterns
+    if (['dev', 'tmp', 'etc', 'usr', 'var', 'bin', 'home'].includes(commandName)) return match
+    // Transform to Codex prompt syntax
+    const normalizedName = normalizeName(commandName)
+    return `/prompts:${normalizedName}`
+  })
+
+  // 3. Transform @agent-name references
+  // Match: @agent-name in text (not emails)
+  const agentRefPattern = /@([a-z][a-z0-9-]*-(?:agent|reviewer|researcher|analyst|specialist|oracle|sentinel|guardian|strategist))/gi
+  result = result.replace(agentRefPattern, (_match, agentName: string) => {
+    const skillName = normalizeName(agentName)
+    return `$${skillName} skill`
+  })
+
+  return result
+}
+
+// Alias for backward compatibility
+const transformTaskCalls = transformContentForCodex
+
 function renderPrompt(command: ClaudeCommand, skillName: string): string {
   const frontmatter: Record<string, unknown> = {
     description: command.description,
     "argument-hint": command.argumentHint,
   }
   const instructions = `Use the $${skillName} skill for this command and follow its instructions.`
-  const body = [instructions, "", command.body].join("\n").trim()
+  // Transform Task calls in prompt body too (not just skill body)
+  const transformedBody = transformTaskCalls(command.body)
+  const body = [instructions, "", transformedBody].join("\n").trim()
   return formatFrontmatter(frontmatter, body)
 }