Add Command Code integration to spec-kit (#4019)

* Add Command Code integration to spec-kit

Adds `command-code` as a built-in skills-based integration so Spec Kit can
be installed into Command Code. Command Code loads agent skills from
`.commandcode/skills/speckit-<name>/SKILL.md` and invokes them in chat as
`$speckit-<command>`.

- New `CommandCodeIntegration` (SkillsIntegration) writing to
  `.commandcode/skills/`; declared multi-install safe (static, isolated
  agent root).
- Register in `_register_builtins()` and the integration catalog.
- Add `command-code` to `DOLLAR_SKILLS_AGENTS` so next-steps guidance
  renders `$speckit-*` invocations.
- Tests: reuse `SkillsIntegrationTests` mixin plus a dollar-invocation
  next-steps test; registry completeness updated.
- Docs: README and docs/reference/integrations.md (supported agents +
  multi-install-safe table).

Co-authored-by: CommandCodeBot <noreply@commandcode.ai>
Assisted-by: Command Code (autonomous)

* Fix issue template agent lists to include command-code

The runtime AGENT_CONFIG now includes command-code, but the GitHub issue
templates and the consistency test's expected key list were not updated,
failing test_issue_template_agent_lists_match_runtime_integrations.

Co-authored-by: CommandCodeBot <noreply@commandcode.ai>
Assisted-by: Command Code (autonomous)

---------

Co-authored-by: CommandCodeBot <noreply@commandcode.ai>

.github/ISSUE_TEMPLATE/agent_request.yml

@@ -8,7 +8,7 @@ body:
       value: |
         Thanks for requesting a new agent! Before submitting, please check if the agent is already supported.
 
-        **Currently supported agents**: Alquimia AI, Amp, Antigravity, Auggie CLI, Claude Code, Cline, CodeBuddy, Codex CLI, Cursor, Devin for Terminal, Factory Droid, Firebender, Forge, Gemini CLI, GitHub Copilot, Goose, Grok Build, Hermes Agent, IBM Bob, Junie, Kilo Code, Kimi Code, Kiro CLI, Lingma, Mistral Vibe, Oh My Pi, opencode, Pi Coding Agent, Qoder CLI, Qwen Code, RovoDev ACLI, SHAI, Tabnine CLI, Trae, ZCode, Zed
+        **Currently supported agents**: Alquimia AI, Amp, Antigravity, Auggie CLI, Claude Code, Cline, CodeBuddy, Codex CLI, Command Code, Cursor, Devin for Terminal, Factory Droid, Firebender, Forge, Gemini CLI, GitHub Copilot, Goose, Grok Build, Hermes Agent, IBM Bob, Junie, Kilo Code, Kimi Code, Kiro CLI, Lingma, Mistral Vibe, Oh My Pi, opencode, Pi Coding Agent, Qoder CLI, Qwen Code, RovoDev ACLI, SHAI, Tabnine CLI, Trae, ZCode, Zed
 
   - type: input
     id: agent-name

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -70,6 +70,7 @@ body:
         - Cline
         - CodeBuddy
         - Codex CLI
+        - Command Code
         - Cursor
         - Devin for Terminal
         - Factory Droid

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -64,6 +64,7 @@ body:
         - Cline
         - CodeBuddy
         - Codex CLI
+        - Command Code
         - Cursor
         - Devin for Terminal
         - Factory Droid