Add /create-capability command for scaffolding capability sets

Introduces a new command that guides users through creating capabilities
for the architecture repository. The command analyzes user descriptions,
recommends appropriate component combinations (skill, command, agent),
gathers necessary information, generates files from templates, and presents
them for approval before creation.

Closes #75

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

commands/create-capability.md

@@ -0,0 +1,123 @@
+---
+description: Create a new capability (skill, command, agent, or a cohesive set) for the architecture repository.
+argument-hint: <description>
+---
+
+# Create Capability
+
+@~/.claude/skills/capability-writing/SKILL.md
+
+Create new capabilities following established patterns. A capability may be a single component or a cohesive set (skill + command + agent).
+
+## Process
+
+1. **Understand the capability**: Analyze "$1" to understand what the user wants to build
+   - What domain or workflow does this cover?
+   - What user need does it address?
+   - What existing capabilities might overlap?
+
+2. **Determine components needed**: Based on the description, recommend which components:
+
+   | Pattern | When to Use |
+   |---------|-------------|
+   | Skill only | Knowledge to apply automatically (reused across commands) |
+   | Command only | User-invoked workflow using existing skills |
+   | Command + Skill | New knowledge + workflow to use it |
+   | Command + Agent | Workflow with isolated worker for complex subtasks |
+   | Full set | New domain expertise + workflow + isolated work |
+
+   Present recommendation with reasoning:
+   ```
+   ## Recommended Components for: $1
+
+   Based on your description, I recommend:
+   - **Skill**: `name` - [why this knowledge is needed]
+   - **Command**: `/name` - [what user action this enables]
+   - **Agent**: `name` - [why isolation/specialization is needed] (optional)
+
+   Reasoning: [explain why this combination fits the need]
+   ```
+
+3. **Gather information**: For each recommended component, ask:
+
+   **For all components:**
+   - Name (kebab-case, descriptive)
+   - Description (one-line summary)
+
+   **For Skills:**
+   - What domain/knowledge does this cover?
+   - What are the key concepts to teach?
+   - What patterns or templates should it include?
+
+   **For Commands:**
+   - What triggers this workflow?
+   - What are the key steps?
+   - What approval points are needed?
+   - What skills should it reference?
+
+   **For Agents:**
+   - What specialized role does this fill?
+   - What skills does it need?
+   - Should it be read-only (no Edit/Write)?
+
+4. **Select appropriate models**:
+
+   | Model | Use For |
+   |-------|---------|
+   | `haiku` | Simple fetch/display commands, formatting tasks |
+   | `sonnet` | Most commands and agents (default) |
+   | `opus` | Deep reasoning, architectural analysis, complex judgment |
+
+   For each component, recommend a model with reasoning.
+
+5. **Generate files**: Create content using templates from capability-writing skill
+
+   Ensure proper inter-references:
+   - Command references skill via `@~/.claude/skills/name/SKILL.md`
+   - Agent lists skills in `skills:` frontmatter (names only, not paths)
+   - Command spawns agent via Task tool if agent is part of the set
+
+6. **Present for approval**: Show all generated files with their full content:
+   ```
+   ## Generated Files
+
+   ### skills/name/SKILL.md
+   [full content]
+
+   ### commands/name.md
+   [full content]
+
+   ### agents/name/AGENT.md (if applicable)
+   [full content]
+
+   Ready to create these files?
+   ```
+
+7. **Create files** in correct locations after approval:
+   - `skills/<name>/SKILL.md`
+   - `commands/<name>.md`
+   - `agents/<name>/AGENT.md`
+
+8. **Report success**:
+   ```
+   ## Capability Created: name
+
+   Files created:
+   - skills/name/SKILL.md
+   - commands/name.md
+   - agents/name/AGENT.md (if applicable)
+
+   Next steps:
+   1. Run `make install` to symlink to ~/.claude/
+   2. Test with: /name (for commands)
+   3. Skills will auto-activate based on context
+   ```
+
+## Guidelines
+
+- Follow all conventions from capability-writing skill
+- Reference existing skills rather than duplicating knowledge
+- Keep components focused - split if scope is too broad
+- Commands should have approval checkpoints before significant actions
+- Default to `sonnet` model unless there's a clear reason for haiku/opus
+- Skills should have descriptive `description` fields for auto-activation