feat(integrations): add Grok Build skills-based integration (#3535)

* feat(integrations): add Grok Build skills-based integration

Add first-class support for xAI Grok Build via SkillsIntegration, installing
speckit skills under .grok/skills and wiring init/invocation/catalog surfaces.

Assisted-by: Grok Build (model: grok-4, supervised)

* test+docs: address Copilot review on Grok multi-install and next steps

Assert init next-steps guidance for Grok (.grok/skills, /speckit-*) and
clarify that multi-install safety is path/manifest isolation, not
agent-context defaults such as shared AGENTS.md.

* fix(integrations): Grok headless --always-approve and isolation paths

Document Grok multi-install isolation as .grok/skills and .grok/rules.
Override build_exec_args to pass --always-approve so non-interactive
dispatch is not blocked at tool permission gates.

* docs(integrations): list only managed .grok/skills for Grok isolation

Multi-install isolation documents Spec Kit-managed paths; Grok only
writes .grok/skills, so drop the read-only .grok/rules entry.

* fix(integrations): always-slash Grok hooks and refresh catalog date

Move grok to ALWAYS_SLASH_AGENTS so hooks never emit /speckit.plan when
ai_skills is missing/false. Update slash-format tests, persist ai_skills
on init, and bump catalog updated_at for the Grok entry.

---------

Co-authored-by: Nate Chadwick <1232206+natechadwick@users.noreply.github.com>
Co-authored-by: test <test@example.com>

src/specify_cli/commands/init.py

@@ -701,6 +701,7 @@ def register(app: typer.Typer) -> None:
         copilot_skill_mode = selected_ai == "copilot" and _is_skills_integration
         devin_skill_mode = selected_ai == "devin"
         zed_skill_mode = selected_ai == "zed" and _is_skills_integration
+        grok_skill_mode = selected_ai == "grok" and _is_skills_integration
         cline_skill_mode = selected_ai == "cline"
         native_skill_mode = (
             codex_skill_mode
@@ -713,6 +714,7 @@ def register(app: typer.Typer) -> None:
             or copilot_skill_mode
             or devin_skill_mode
             or zed_skill_mode
+            or grok_skill_mode
         )
 
         if codex_skill_mode:
@@ -745,6 +747,11 @@ def register(app: typer.Typer) -> None:
                 f"{step_num}. Start Zed in this project directory; spec-kit skills were installed to [cyan].agents/skills[/cyan]"
             )
             step_num += 1
+        if grok_skill_mode:
+            steps_lines.append(
+                f"{step_num}. Start Grok Build in this project directory; spec-kit skills were installed to [cyan].grok/skills[/cyan]"
+            )
+            step_num += 1
         usage_label = "skills" if native_skill_mode else "slash commands"
 
         from .._invocation_style import (