V4.1 major revision to docs. Removed all obsolete documents, updated v4.2 implementation scope and plan.

docs/ver4/error_handling_v4.md

@@ -1,13 +1,17 @@
 # Error Handling Policy (Version 4)
 
-This document defines the canonical error-handling policy for the document transcription system.
+This document defines the Version 4 taxonomy, contracts, and framework behavior used to satisfy the cross-version [Error Handling invariant](../invariant/error_handling.md).
 
-## Error Handling Objectives
+## Invariant Alignment
 
-- Make failures visible in clear, actionable language at both the document and page levels.
-- Support isolated failure handling in multi-page jobs so one failing page does not invalidate successful pages.
-- Preserve diagnostic detail for validation failures, provider failures, and policy conflicts.
-- Ensure consistent error envelope structure across API, UI, service, and worker boundaries.
+Version 4 implements the invariant through:
+
+- The shared error taxonomy below.
+- Structured error envelopes with correlation IDs.
+- Page-level failure isolation and explicit aggregate job status.
+- Atomic relationship and classification writes.
+- Consistent translation across API, UI, service, worker, persistence, and provider boundaries.
+- Bounded retry guidance based on category and idempotency.
 
 ## Scope and Authority
 
@@ -104,6 +108,7 @@ HTTP status mappings:
 
 ## Related Local References
 
+- [Error Handling Invariant](../invariant/error_handling.md)
 - [System Overview](index_v4.md)
 - [System Requirements](requirements_v4.md)
 - [Data Model](schema_v4.md)