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.md

@@ -4,10 +4,11 @@
 
 Schema: `info-tech-canon.retrieval-index.v1`
 Infospace: `canon`
-Items: **68**
+Items: **70**
 
 ## Common Distinctions
 
+- **Interface deprecation vs retirement vs removal**: 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. Sources: `practice-pattern/interface-deprecation-strangler`
 - **Actor vs Subject vs Principal**: Use actor for the acting entity in a context, subject for the entity a policy evaluates, and principal for the authenticated identity bound to access decisions. Sources: `model/organization`, `model/access-control`, `standard/caring`
 - **Organization Role vs AccessRole vs CARING role**: Organization roles describe responsibility or position; access roles describe permissions; CARING roles classify access-governance needs and analysis. Sources: `model/organization`, `model/access-control`, `standard/caring`
 - **Policy vs Control vs Evidence**: Policy states intent or rule, control implements or enforces that rule, and evidence records why the claim should be trusted. Sources: `model/governance`, `model/security`, `model/observability`
@@ -455,6 +456,16 @@ Items: **68**
 - Imports and anchors: `model/governance`, `model/task`
 - Owned concepts: `Intent Scope Purposes Pattern`, `IntentScopePurposePattern`
 
+### InterfaceDeprecationStrangler
+
+- ID: `practice-pattern/interface-deprecation-strangler`
+- Kind: `practice-pattern`
+- Canonical path: `patterns/InterfaceDeprecationStrangler.md`
+- Source path: `patterns/InterfaceDeprecationStrangler.md`
+- Summary: Reusable canon PracticePattern: InterfaceDeprecationStrangler.
+- Imports and anchors: `model/devsecops`, `model/governance`, `model/observability`, `scheme/practice-pattern`
+- Owned concepts: `InterfaceDeprecationStrangler`
+
 ### Intake and Assimilation Practice
 
 - ID: `practice/intake-and-assimilation`
@@ -535,6 +546,16 @@ Items: **68**
 - Imports and anchors: `model/purpose-demand-extension`, `model/task`
 - Owned concepts: `Consumer Alignment Workplan Template`
 
+### PracticePattern Scheme
+
+- ID: `scheme/practice-pattern`
+- Kind: `practice-pattern-scheme`
+- Canonical path: `patterns/PracticePatternScheme.md`
+- Source path: `patterns/PracticePatternScheme.md`
+- Summary: Contract for canon PracticePattern artifacts: PracticePattern Scheme.
+- Imports and anchors: `kernel/itc-core`
+- Owned concepts: `PatternLanguage`, `PracticePattern`, `PracticePattern Scheme`
+
 ### Namespace Per Tenant Control
 
 - ID: `small-saas/control/namespace-per-tenant`