fix(integrations): declare PiIntegration multi_install_safe

PiIntegration writes only to its isolated, static root .pi/prompts,
disjoint from every other integration, yet never declared
multi_install_safe — so it inherited the IntegrationBase default False,
leaving `specify integration status` in a permanent unsafe-multi-install
ERROR state when pi is co-installed alongside another agent.

Add `multi_install_safe = True`, mirroring the isolated MarkdownIntegration
cohort (qwen, shai, qodercli) and the kiro-cli #3471 fix. The parametrized
registry isolation contracts auto-include pi and pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jawwad-ali

src/specify_cli/integrations/pi/__init__.py

@@ -18,3 +18,4 @@ class PiIntegration(MarkdownIntegration):
         "args": "$ARGUMENTS",
         "extension": ".md",
     }
+    multi_install_safe = True

tests/integrations/test_integration_pi.py

@@ -1,5 +1,7 @@
 """Tests for PiIntegration."""
 
+from specify_cli.integrations import get_integration
+
 from .test_integration_base_markdown import MarkdownIntegrationTests
 
 
@@ -8,3 +10,9 @@ class TestPiIntegration(MarkdownIntegrationTests):
     FOLDER = ".pi/"
     COMMANDS_SUBDIR = "prompts"
     REGISTRAR_DIR = ".pi/prompts"
+
+    def test_multi_install_safe(self):
+        # Pi writes only to its isolated, static root .pi/prompts, disjoint from
+        # every other integration, so it must be co-install safe (mirrors
+        # qwen/shai/qodercli and the kiro-cli #3471 precedent).
+        assert get_integration(self.KEY).multi_install_safe is True