fix(domain): correct invariant precedence chain to include action scope

The invariant precedence chain is four-tier per specification §92:
plan > action > project > global

This fix updates:
1. Module docstring in invariant.py to document the correct four-tier precedence
2. InvariantScope class docstring to reflect PLAN > ACTION > PROJECT > GLOBAL
3. merge_invariants() function to accept action_invariants parameter
4. InvariantSet.merge() class method to accept and pass action_invariants
5. InvariantService.get_effective_invariants() to collect and pass action invariants
6. BDD test steps to include action invariants in merge operations
7. Benchmark suite to include action invariants in performance tests
8. Robot Framework helper to pass action_invariants to merge functions
9. CHANGELOG.md entry under [Unreleased]/### Fixed section
10. CONTRIBUTORS.md entry documenting HAL 9000 contribution

All docstrings now correctly document the four-tier precedence chain,
and the merge logic properly handles action-scope invariants between
plan and project scopes.

ISSUES CLOSED: #9003

benchmarks/invariant_merge_bench.py

@@ -69,12 +69,13 @@ class MergeSmallSuite:
     def setup(self) -> None:
         """Create small invariant lists."""
         self.plan = _make_invariants(InvariantScope.PLAN, 3)
+        self.action = _make_invariants(InvariantScope.ACTION, 2)
         self.project = _make_invariants(InvariantScope.PROJECT, 5)
         self.global_invs = _make_invariants(InvariantScope.GLOBAL, 5)
 
     def time_merge_small(self) -> None:
-        """Benchmark merge with ~13 invariants."""
-        merge_invariants(self.plan, [], self.project, self.global_invs)
+        """Benchmark merge with ~15 invariants."""
+        merge_invariants(self.plan, self.action, self.project, self.global_invs)
 
 
 class MergeMediumSuite:
@@ -83,12 +84,13 @@ class MergeMediumSuite:
     def setup(self) -> None:
         """Create medium invariant lists."""
         self.plan = _make_invariants(InvariantScope.PLAN, 10)
+        self.action = _make_invariants(InvariantScope.ACTION, 5)
         self.project = _make_invariants(InvariantScope.PROJECT, 20)
         self.global_invs = _make_invariants(InvariantScope.GLOBAL, 20)
 
     def time_merge_medium(self) -> None:
-        """Benchmark merge with ~50 invariants."""
-        merge_invariants(self.plan, [], self.project, self.global_invs)
+        """Benchmark merge with ~55 invariants."""
+        merge_invariants(self.plan, self.action, self.project, self.global_invs)
 
 
 class MergeLargeSuite:
@@ -97,12 +99,13 @@ class MergeLargeSuite:
     def setup(self) -> None:
         """Create large invariant lists."""
         self.plan = _make_invariants(InvariantScope.PLAN, 50)
+        self.action = _make_invariants(InvariantScope.ACTION, 25)
         self.project = _make_invariants(InvariantScope.PROJECT, 100)
         self.global_invs = _make_invariants(InvariantScope.GLOBAL, 100)
 
     def time_merge_large(self) -> None:
-        """Benchmark merge with ~250 invariants."""
-        merge_invariants(self.plan, [], self.project, self.global_invs)
+        """Benchmark merge with ~275 invariants."""
+        merge_invariants(self.plan, self.action, self.project, self.global_invs)
 
 
 class MergeDeduplicationSuite:
@@ -118,6 +121,14 @@ class MergeDeduplicationSuite:
             )
             for i in range(20)
         ]
+        self.action = [
+            Invariant(
+                text=f"Shared constraint {i}",
+                scope=InvariantScope.ACTION,
+                source_name="action-001",
+            )
+            for i in range(20)
+        ]
         self.project = [
             Invariant(
                 text=f"Shared constraint {i}",
@@ -136,8 +147,8 @@ class MergeDeduplicationSuite:
         ]
 
     def time_merge_dedup(self) -> None:
-        """Benchmark merge with 60 invariants, all duplicates."""
-        merge_invariants(self.plan, [], self.project, self.global_invs)
+        """Benchmark merge with 80 invariants, all duplicates."""
+        merge_invariants(self.plan, self.action, self.project, self.global_invs)
 
 
 class InvariantSetMergeSuite:
@@ -146,12 +157,13 @@ class InvariantSetMergeSuite:
     def setup(self) -> None:
         """Create invariant lists."""
         self.plan = _make_invariants(InvariantScope.PLAN, 5)
+        self.action = _make_invariants(InvariantScope.ACTION, 3)
         self.project = _make_invariants(InvariantScope.PROJECT, 10)
         self.global_invs = _make_invariants(InvariantScope.GLOBAL, 10)
 
     def time_invariant_set_merge(self) -> None:
         """Benchmark InvariantSet.merge()."""
-        InvariantSet.merge(self.plan, [], self.project, self.global_invs)
+        InvariantSet.merge(self.plan, self.action, self.project, self.global_invs)
 
 
 class ServiceEffectiveSuite:
@@ -164,9 +176,15 @@ class ServiceEffectiveSuite:
             self.service.add_invariant(f"Global {i}", InvariantScope.GLOBAL, "system")
         for i in range(10):
             self.service.add_invariant(f"Project {i}", InvariantScope.PROJECT, "myapp")
+        for i in range(5):
+            self.service.add_invariant(
+                f"Action {i}", InvariantScope.ACTION, "action-001"
+            )
         for i in range(5):
             self.service.add_invariant(f"Plan {i}", InvariantScope.PLAN, "plan-001")
 
     def time_get_effective(self) -> None:
         """Benchmark get_effective_invariants()."""
-        self.service.get_effective_invariants(plan_id="plan-001", project_name="myapp")
+        self.service.get_effective_invariants(
+            plan_id="plan-001", project_name="myapp", action_name="action-001"
+        )

features/steps/invariant_models_steps.py

@@ -430,6 +430,7 @@ def step_service_all_scopes(context):
     context.service = InvariantService()
     context.service.add_invariant("Global rule", InvariantScope.GLOBAL, "system")
     context.service.add_invariant("Project rule", InvariantScope.PROJECT, "proj1")
+    context.service.add_invariant("Action rule", InvariantScope.ACTION, "action1")
     context.service.add_invariant("Plan rule", InvariantScope.PLAN, "plan1")