Spec-kit commands consume significant portion of context window in every session

### Problem

When spec-kit is initialized, slash commands are added to `.claude/commands/` (or other agent's equivalent locations).

If others work like Claude Code, these commands are loaded into the agent's context window for **every chat session**, regardless of whether spec-kit is being actively used.

This creates a significant "context tax" that reduces the available working space for actual development tasks.

### Context Window Consumption

Based on `/context` output in Claude Code, spec-kit commands consume approximately **18.6k tokens**:

| Command | Tokens |
|---------|--------|
| speckit.checklist | 4.2k |
| speckit.specify | 3.1k |
| speckit.implement | 3.1k |
| speckit.clarify | 2.8k |
| speckit.analyze | 1.8k |
| speckit.tasks | 1.5k |
| speckit.constitution | 1.2k |
| speckit.plan | 690 |
| speckit.taskstoissues | 218 |

### Impact Across Supported Platforms

The ~18.6k token consumption impacts others in this way:

| Platform | Context Window | spec-kit Consumption |
|-----------------------------------|-----------------|----------------------|
| Cursor (default chat) | ~20k tokens | ~93% |
| Windsurf (typical) | 32-100k tokens | ~19-58% |
| GitHub Copilot (standard) | 64k tokens | ~29% |
| GitHub Copilot (VS Code Insiders) | 128k tokens | ~14.5% |
| Codex CLI (OpenAI) | 192-272k tokens | ~7-10% |
| Claude Code | 200k tokens | ~9.3% |
| Cursor (max mode) | 200k tokens | ~9.3% |
| Amazon Q Developer CLI | 200k tokens | ~9.3% |
| Amp (Sourcegraph) | 200-432k tokens | ~4-9% |
| Gemini CLI | 1M tokens | ~1.9% |
| Roo Code | model-dependent | varies |

The impact is most severe on:
- **Cursor default chat (~20k)**: spec-kit would consume nearly the entire context
- **GitHub Copilot standard (64k)**: nearly a third of available context
- **Windsurf**: varies by model, but often significant

### Why This Matters

Context window space is a finite and valuable resource. Every token consumed by spec-kit commands is a token unavailable for:

- **Code context**: Less room for file contents, reducing the agent's ability to understand the codebase
- **Conversation history**: Earlier parts of the conversation get truncated sooner
- **Agent reasoning**: Less space for the agent to think through complex problems

Users who have spec-kit installed but aren't actively using it for a particular task are paying this cost with no benefit.

### Possible Mitigation

One simple option might be `specify disable` / `specify enable` commands that move command files to/from a backup location (e.g., `.claude/commands-disabled/`), allowing users to toggle spec-kit out of context when not in use.

However, I imagine there may be better architectural solutions the maintainers could consider.

### My Environment

- Claude Code with Max plan (200k context)