feat(tools): add slashcommand tool for executing slash commands

Provides 'slashcommand' tool that executes commands loaded by command-loader.
Handles shell injection and file reference resolution.

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/tools/slashcommand/index.ts

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+export * from "./types"
+export { slashcommand } from "./tools"

src/tools/slashcommand/tools.ts

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+import { tool } from "@opencode-ai/plugin"
+import { existsSync, readdirSync, readFileSync } from "fs"
+import { homedir } from "os"
+import { join, basename, dirname } from "path"
+import { parseFrontmatter, resolveCommandsInText, resolveFileReferencesInText, sanitizeModelField } from "../../shared"
+import type { CommandScope, CommandMetadata, CommandInfo } from "./types"
+
+function discoverCommandsFromDir(commandsDir: string, scope: CommandScope): CommandInfo[] {
+  if (!existsSync(commandsDir)) {
+    return []
+  }
+
+  const entries = readdirSync(commandsDir, { withFileTypes: true })
+  const commands: CommandInfo[] = []
+
+  for (const entry of entries) {
+    if (entry.name.startsWith(".")) continue
+    if (!entry.name.endsWith(".md")) continue
+    if (!entry.isFile()) continue
+
+    const commandPath = join(commandsDir, entry.name)
+    const commandName = basename(entry.name, ".md")
+
+    try {
+      const content = readFileSync(commandPath, "utf-8")
+      const { data, body } = parseFrontmatter(content)
+
+      const metadata: CommandMetadata = {
+        name: commandName,
+        description: data.description || "",
+        argumentHint: data["argument-hint"],
+        model: sanitizeModelField(data.model),
+        agent: data.agent,
+        subtask: Boolean(data.subtask),
+      }
+
+      commands.push({
+        name: commandName,
+        path: commandPath,
+        metadata,
+        content: body,
+        scope,
+      })
+    } catch {
+      continue
+    }
+  }
+
+  return commands
+}
+
+function discoverCommandsSync(): CommandInfo[] {
+  const userCommandsDir = join(homedir(), ".claude", "commands")
+  const projectCommandsDir = join(process.cwd(), ".claude", "commands")
+  const opencodeGlobalDir = join(homedir(), ".config", "opencode", "command")
+  const opencodeProjectDir = join(process.cwd(), ".opencode", "command")
+
+  const userCommands = discoverCommandsFromDir(userCommandsDir, "user")
+  const opencodeGlobalCommands = discoverCommandsFromDir(opencodeGlobalDir, "opencode")
+  const projectCommands = discoverCommandsFromDir(projectCommandsDir, "project")
+  const opencodeProjectCommands = discoverCommandsFromDir(opencodeProjectDir, "opencode-project")
+
+  return [...opencodeProjectCommands, ...projectCommands, ...opencodeGlobalCommands, ...userCommands]
+}
+
+const availableCommands = discoverCommandsSync()
+const commandListForDescription = availableCommands
+  .map((cmd) => {
+    const hint = cmd.metadata.argumentHint ? ` ${cmd.metadata.argumentHint}` : ""
+    return `- /${cmd.name}${hint}: ${cmd.metadata.description} (${cmd.scope})`
+  })
+  .join("\n")
+
+async function formatLoadedCommand(cmd: CommandInfo): Promise<string> {
+  const sections: string[] = []
+
+  sections.push(`# /${cmd.name} Command\n`)
+
+  if (cmd.metadata.description) {
+    sections.push(`**Description**: ${cmd.metadata.description}\n`)
+  }
+
+  if (cmd.metadata.argumentHint) {
+    sections.push(`**Usage**: /${cmd.name} ${cmd.metadata.argumentHint}\n`)
+  }
+
+  if (cmd.metadata.model) {
+    sections.push(`**Model**: ${cmd.metadata.model}\n`)
+  }
+
+  if (cmd.metadata.agent) {
+    sections.push(`**Agent**: ${cmd.metadata.agent}\n`)
+  }
+
+  if (cmd.metadata.subtask) {
+    sections.push(`**Subtask**: true\n`)
+  }
+
+  sections.push(`**Scope**: ${cmd.scope}\n`)
+  sections.push("---\n")
+  sections.push("## Command Instructions\n")
+
+  const commandDir = dirname(cmd.path)
+  const withFileRefs = await resolveFileReferencesInText(cmd.content, commandDir)
+  const resolvedContent = await resolveCommandsInText(withFileRefs)
+  sections.push(resolvedContent.trim())
+
+  return sections.join("\n")
+}
+
+function formatCommandList(commands: CommandInfo[]): string {
+  if (commands.length === 0) {
+    return "No commands found."
+  }
+
+  const lines = ["# Available Commands\n"]
+
+  for (const cmd of commands) {
+    const hint = cmd.metadata.argumentHint ? ` ${cmd.metadata.argumentHint}` : ""
+    lines.push(
+      `- **/${cmd.name}${hint}**: ${cmd.metadata.description || "(no description)"} (${cmd.scope})`
+    )
+  }
+
+  lines.push(`\n**Total**: ${commands.length} commands`)
+  return lines.join("\n")
+}
+
+export const slashcommand = tool({
+  description: `Execute a slash command within the main conversation.
+
+When you use this tool, the slash command gets expanded to a full prompt that provides detailed instructions on how to complete the task.
+
+How slash commands work:
+- Invoke commands using this tool with the command name (without arguments)
+- The command's prompt will expand and provide detailed instructions
+- Arguments from user input should be passed separately
+
+Important:
+- Only use commands listed in Available Commands below
+- Do not invoke a command that is already running
+- **CRITICAL**: When user's message starts with '/' (e.g., "/commit", "/plan"), you MUST immediately invoke this tool with that command. Do NOT attempt to handle the command manually.
+
+Commands are loaded from (priority order, highest wins):
+- .opencode/command/ (opencode-project - OpenCode project-specific commands)
+- ./.claude/commands/ (project - Claude Code project-specific commands)
+- ~/.config/opencode/command/ (opencode - OpenCode global commands)
+- ~/.claude/commands/ (user - Claude Code global commands)
+
+Each command is a markdown file with:
+- YAML frontmatter: description, argument-hint, model, agent, subtask (optional)
+- Markdown body: The command instructions/prompt
+- File references: @path/to/file (relative to command file location)
+- Shell injection: \`!\`command\`\` (executes and injects output)
+
+Available Commands:
+${commandListForDescription}`,
+
+  args: {
+    command: tool.schema
+      .string()
+      .describe(
+        "The slash command to execute (without the leading slash). E.g., 'commit', 'plan', 'execute'."
+      ),
+  },
+
+  async execute(args) {
+    const commands = discoverCommandsSync()
+
+    if (!args.command) {
+      return formatCommandList(commands) + "\n\nProvide a command name to execute."
+    }
+
+    const cmdName = args.command.replace(/^\//, "")
+
+    const exactMatch = commands.find(
+      (cmd) => cmd.name.toLowerCase() === cmdName.toLowerCase()
+    )
+
+    if (exactMatch) {
+      return await formatLoadedCommand(exactMatch)
+    }
+
+    const partialMatches = commands.filter((cmd) =>
+      cmd.name.toLowerCase().includes(cmdName.toLowerCase())
+    )
+
+    if (partialMatches.length > 0) {
+      const matchList = partialMatches.map((cmd) => `/${cmd.name}`).join(", ")
+      return (
+        `No exact match for "/${cmdName}". Did you mean: ${matchList}?\n\n` +
+        formatCommandList(commands)
+      )
+    }
+
+    return (
+      `Command "/${cmdName}" not found.\n\n` +
+      formatCommandList(commands) +
+      "\n\nTry a different command name."
+    )
+  },
+})

src/tools/slashcommand/types.ts

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+export type CommandScope = "user" | "project" | "opencode" | "opencode-project"
+
+export interface CommandMetadata {
+  name: string
+  description: string
+  argumentHint?: string
+  model?: string
+  agent?: string
+  subtask?: boolean
+}
+
+export interface CommandInfo {
+  name: string
+  path: string
+  metadata: CommandMetadata
+  content: string
+  scope: CommandScope
+}