docs(command-development): clarify model field accepts full model strings (#57)

## Summary

Clarifies that the `model` frontmatter field in slash commands accepts
both shorthand values and full model IDs.

## Problem

Fixes #49

The command-development skill documentation only showed shorthand model
values (`sonnet`, `opus`, `haiku`), but official Claude docs show full
model IDs are also valid. This caused potential confusion about accepted
formats.

## Solution

Updated documentation to explicitly show both formats:
- Shorthand: `sonnet`, `opus`, `haiku`
- Full model ID: `claude-sonnet-4-5-20250929`,
`claude-haiku-4-5-20251001`, etc.

Added clarification that shorthand names use the current default version
of each model family.

### Alternatives Considered

- Only update the reference file: Decided to update both SKILL.md and
frontmatter-reference.md for consistency
- Use older model IDs from the issue: Updated to use current 4.5 model
IDs (as of December 2025)

## Changes

- `skills/command-development/references/frontmatter-reference.md`:
Updated model field values and validation fix text
- `skills/command-development/SKILL.md`: Updated model field type and
values

## Testing

- [x] Linting passes (`markdownlint`)
- [x] Documentation is accurate per official Claude docs

---
🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

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

Author: sjnims

plugins/plugin-dev/skills/command-development/SKILL.md

@@ -155,7 +155,8 @@ allowed-tools: Read, Write, Edit, Bash(git:*)
 ### model
 
 **Purpose:** Specify model for command execution
-**Type:** String (sonnet, opus, haiku)
+**Type:** String
+**Values:** Shorthand (`sonnet`, `opus`, `haiku`) or full model ID (e.g., `claude-sonnet-4-5-20250929`)
 **Default:** Inherits from conversation
 
 ```yaml
@@ -170,6 +171,8 @@ model: haiku
 - `sonnet` - Standard workflows
 - `opus` - Complex analysis
 
+Shorthand names use the current default version of each model family.
+
 ### argument-hint
 
 **Purpose:** Document expected arguments for autocomplete

plugins/plugin-dev/skills/command-development/references/frontmatter-reference.md

@@ -132,7 +132,14 @@ allowed-tools: "*"
 **Type:** String
 **Required:** No
 **Default:** Inherits from conversation
-**Values:** `sonnet`, `opus`, `haiku`
+**Values:**
+
+- Shorthand: `sonnet`, `opus`, `haiku`
+- Full model ID: `claude-sonnet-4-5-20250929`, `claude-haiku-4-5-20251001`, etc.
+
+Both formats are accepted. Shorthand names use the current default version of each model family.
+
+> **Note:** Model ID examples above reflect December 2025 releases. Anthropic releases new model versions periodically. For current model IDs, consult [Claude Models Overview](https://docs.anthropic.com/en/docs/about-claude/models).
 
 **Purpose:** Specify which Claude model executes the command
 
@@ -440,7 +447,7 @@ allowed-tools: Bash  # ❌ Missing command filter
 model: gpt4  # ❌ Not a valid Claude model
 ```
 
-**Fix:** Use `sonnet`, `opus`, or `haiku`
+**Fix:** Use shorthand (`sonnet`, `opus`, `haiku`) or full model ID (e.g., `claude-sonnet-4-5-20250929`)
 
 ### Validation Checklist