chore: Archive update-slash-commands-session change

- Move change to archive/2025-12-24-update-slash-commands-session
- Create specs/slash-commands/spec.md with 10 requirements

openspec/changes/archive/2025-12-24-update-slash-commands-session/specs/slash-commands/spec.md

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+## ADDED Requirements
+
+### Requirement: Slash Command Types Documentation
+
+The documentation SHALL describe the four types of slash commands:
+1. Built-in commands provided by Claude Code
+2. Custom user-defined commands (project and personal)
+3. Plugin commands
+4. MCP (Model Context Protocol) slash commands
+
+#### Scenario: User learns about command types
+- **WHEN** a user reads the slash commands documentation
+- **THEN** they understand the different types of slash commands available
+- **AND** they know when to use each type
+
+---
+
+### Requirement: Built-in Commands Reference
+
+The documentation SHALL include a comprehensive reference table of all built-in slash commands with their purposes, including but not limited to:
+- `/add-dir` - Add additional working directories
+- `/agents` - Manage custom AI subagents
+- `/clear` - Clear conversation history
+- `/compact` - Compact conversation with optional focus instructions
+- `/config` - Open Settings interface
+- `/context` - Visualize current context usage
+- `/cost` - Show token usage statistics
+- `/doctor` - Check installation health
+- `/export` - Export conversation to file or clipboard
+- `/help` - Get usage help
+- `/hooks` - Manage hook configurations
+- `/init` - Initialize project with CLAUDE.md
+- `/mcp` - Manage MCP server connections
+- `/memory` - Edit CLAUDE.md memory files
+- `/model` - Select or change AI model
+- `/permissions` - View or update permissions
+- `/resume` - Resume conversation by ID or name
+- `/review` - Request code review
+- `/sandbox` - Enable sandboxed bash tool
+- `/vim` - Enter vim mode
+
+#### Scenario: User finds built-in command
+- **WHEN** a user needs to perform a common operation
+- **THEN** they can find the appropriate built-in command in the reference table
+- **AND** they understand what the command does
+
+---
+
+### Requirement: Argument Handling
+
+The documentation SHALL explain both argument handling methods:
+1. `$ARGUMENTS` - Receives all arguments as a single string
+2. `$1`, `$2`, `$3`, etc. - Individual positional arguments
+
+#### Scenario: User uses $ARGUMENTS placeholder
+- **WHEN** a user creates a command with `$ARGUMENTS` placeholder
+- **AND** invokes it with `/fix-issue 123 high-priority`
+- **THEN** `$ARGUMENTS` contains "123 high-priority"
+
+#### Scenario: User uses positional arguments
+- **WHEN** a user creates a command with `$1`, `$2`, `$3` placeholders
+- **AND** invokes it with `/review-pr 456 high alice`
+- **THEN** `$1` is "456", `$2` is "high", `$3` is "alice"
+
+---
+
+### Requirement: Bash Command Execution
+
+The documentation SHALL explain the `!` prefix for executing bash commands within slash command files before the command runs.
+
+#### Scenario: User includes dynamic context
+- **WHEN** a user adds `!git status` in their command file
+- **THEN** the git status output is included in the command context
+- **AND** Claude receives the current repository state
+
+---
+
+### Requirement: File Reference Syntax
+
+The documentation SHALL explain the `@` prefix for including file contents in slash commands.
+
+#### Scenario: User references a file
+- **WHEN** a user adds `@src/utils/helpers.js` in their command file
+- **THEN** the contents of that file are included in the command context
+
+---
+
+### Requirement: Frontmatter Fields
+
+The documentation SHALL document all supported frontmatter fields:
+- `allowed-tools` - List of tools the command can use
+- `argument-hint` - Expected arguments for auto-completion
+- `description` - Brief description of the command
+- `model` - Specific model to use for this command
+- `disable-model-invocation` - Prevent SlashCommand tool from calling this command
+
+#### Scenario: User creates command with frontmatter
+- **WHEN** a user creates a command with frontmatter fields
+- **THEN** Claude Code respects those configuration options
+- **AND** the command behaves according to the specified settings
+
+---
+
+### Requirement: Plugin Commands Documentation
+
+The documentation SHALL explain the plugin command format: `/plugin-name:command-name` or simply `/command-name` when there are no naming conflicts.
+
+#### Scenario: User invokes plugin command
+- **WHEN** a user types `/frontend-design:frontend-design`
+- **THEN** the corresponding plugin command executes
+
+---
+
+### Requirement: MCP Slash Commands Documentation
+
+The documentation SHALL explain the MCP slash command format: `/mcp__<server-name>__<prompt-name> [arguments]`
+
+#### Scenario: User invokes MCP command
+- **WHEN** a user types `/mcp__github__list_prs`
+- **THEN** the MCP server's prompt is executed
+
+---
+
+### Requirement: SlashCommand Tool Documentation
+
+The documentation SHALL explain how Claude can programmatically invoke slash commands using the SlashCommand tool, including:
+- How to enable this via prompt or CLAUDE.md references
+- How to disable via permissions
+- The character budget limit (default 15,000, configurable via `SLASH_COMMAND_TOOL_CHAR_BUDGET`)
+
+#### Scenario: User enables programmatic invocation
+- **WHEN** a user adds "Run /write-unit-test when writing tests" to CLAUDE.md
+- **THEN** Claude can automatically invoke that command when appropriate
+
+---
+
+### Requirement: Skills vs Slash Commands Comparison
+
+The documentation SHALL include a comparison table helping users choose between Skills and Slash Commands based on:
+- Best use cases for each
+- File structure differences
+- Invocation method (explicit vs automatic)
+- Complexity level
+
+#### Scenario: User decides between skill and command
+- **WHEN** a user needs to create a reusable capability
+- **THEN** they can use the comparison to decide whether a slash command or skill is more appropriate