feat(ITC-WP-0016): establish PracticePattern language

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a025c2-407a-7a32-b40a-f37a52f03f62

infospace/agent/retrieval-index.yaml

@@ -1,6 +1,6 @@
 schema: info-tech-canon.retrieval-index.v1
 infospace: canon
-item_count: 68
+item_count: 70
 items:
 - id: assimilation/it-capability-canon
   kind: assimilation
@@ -973,6 +973,29 @@ items:
   - type: uses
     target: model/task
   warnings: []
+- id: practice-pattern/interface-deprecation-strangler
+  kind: practice-pattern
+  title: InterfaceDeprecationStrangler
+  canonical_path: patterns/InterfaceDeprecationStrangler.md
+  source_path: patterns/InterfaceDeprecationStrangler.md
+  summary: 'Reusable canon PracticePattern: InterfaceDeprecationStrangler.'
+  owned_concepts:
+  - InterfaceDeprecationStrangler
+  imports:
+  - model/devsecops
+  - model/governance
+  - model/observability
+  - scheme/practice-pattern
+  relationships:
+  - type: conforms_to
+    target: scheme/practice-pattern
+  - type: uses
+    target: model/governance
+  - type: uses
+    target: model/observability
+  - type: uses
+    target: model/devsecops
+  warnings: []
 - id: practice/intake-and-assimilation
   kind: practice
   title: Intake and Assimilation Practice
@@ -1210,6 +1233,22 @@ items:
   - type: uses
     target: model/purpose-demand-extension
   warnings: []
+- id: scheme/practice-pattern
+  kind: practice-pattern-scheme
+  title: PracticePattern Scheme
+  canonical_path: patterns/PracticePatternScheme.md
+  source_path: patterns/PracticePatternScheme.md
+  summary: 'Contract for canon PracticePattern artifacts: PracticePattern Scheme.'
+  owned_concepts:
+  - PatternLanguage
+  - PracticePattern
+  - PracticePattern Scheme
+  imports:
+  - kernel/itc-core
+  relationships:
+  - type: conforms_to
+    target: kernel/itc-core
+  warnings: []
 - id: small-saas/control/namespace-per-tenant
   kind: profile-artifact
   title: Namespace Per Tenant Control
@@ -1584,6 +1623,13 @@ items:
     target: model/task
   warnings: []
 common_distinctions:
+- id: interface-deprecation-retirement-removal
+  title: Interface deprecation vs retirement vs removal
+  summary: Deprecation guides and observes callers, retirement ends legacy behavior
+    while retaining a metered tombstone, and removal deletes that tombstone only after
+    the evidence gate passes.
+  source_artifacts:
+  - practice-pattern/interface-deprecation-strangler
 - id: actor-subject-principal
   title: Actor vs Subject vs Principal
   summary: Use actor for the acting entity in a context, subject for the entity a