fix(integrations): migrate Antigravity (agy) layout to .agents/ and deprecate --skills (#2276)

* refactor(agy): update storage directory from .agent to .agents

* feat: update Antigravity integration to use .agents/ directory layout and add version compatibility warnings

* Apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* refactor: remove deprecated --skills flag from AgyIntegration and update related test assertions

* Update src/specify_cli/integrations/agy/__init__.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* refactor: update Antigravity integration requirement to v1.20.5 and remove obsolete tests

* test: update skills directory path from .agent to .agents in preset restoration test

* Update tests/integrations/test_integration_agy.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update tests/integrations/test_integration_agy.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/specify_cli/integrations/agy/__init__.py

@@ -1,13 +1,18 @@
 """Antigravity (agy) integration — skills-based agent.
 
-Antigravity uses ``.agent/skills/speckit-<name>/SKILL.md`` layout.
-Explicit command support was deprecated in version 1.20.5;
-``--skills`` defaults to ``True``.
+Antigravity uses ``.agents/skills/speckit-<name>/SKILL.md`` layout (enforced since v1.20.5).
 """
 
 from __future__ import annotations
 
-from ..base import IntegrationOption, SkillsIntegration
+from pathlib import Path
+from typing import TYPE_CHECKING, Any
+
+from ..base import SkillsIntegration
+
+if TYPE_CHECKING:
+    from ..manifest import IntegrationManifest
+
 
 
 class AgyIntegration(SkillsIntegration):
@@ -16,26 +21,32 @@ class AgyIntegration(SkillsIntegration):
     key = "agy"
     config = {
         "name": "Antigravity",
-        "folder": ".agent/",
+        "folder": ".agents/",
         "commands_subdir": "skills",
         "install_url": None,
         "requires_cli": False,
     }
     registrar_config = {
-        "dir": ".agent/skills",
+        "dir": ".agents/skills",
         "format": "markdown",
         "args": "$ARGUMENTS",
         "extension": "/SKILL.md",
     }
     context_file = "AGENTS.md"
 
-    @classmethod
-    def options(cls) -> list[IntegrationOption]:
-        return [
-            IntegrationOption(
-                "--skills",
-                is_flag=True,
-                default=True,
-                help="Install as agent skills (default for Antigravity since v1.20.5)",
-            ),
-        ]
+    def setup(
+        self,
+        project_root: Path,
+        manifest: IntegrationManifest,
+        parsed_options: dict[str, Any] | None = None,
+        **opts: Any,
+    ) -> list[Path]:
+        import click
+
+        click.secho(
+            "Warning: The .agents/ layout requires Antigravity v1.20.5 or newer. "
+            "Please ensure your agy installation is up to date.",
+            fg="yellow",
+            err=True,
+        )
+        return super().setup(project_root, manifest, parsed_options=parsed_options, **opts)