Document invocation reporting contracts

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Invocation reporting implementation plan
 
-Status: Stages 1–18 complete. Stage 19 is next.
+Status: Stages 1–19 complete. Stage 20 is next.
 
 ## Objective and authority
 
@@ -719,7 +719,7 @@ on either optional integration module.
 
 ## Stage 19: Update canonical documentation and compatibility guidance
 
-Status: pending.
+Status: complete.
 
 1. Update public Go declarations/GoDoc for exact reporter, outcome, provider,
    lifecycle, cause, and presentation-observation contracts. Describe callback
@@ -749,6 +749,15 @@ Validation: review prose against implemented behavior, check local links and
 fragments, and run the Markdown whitespace checks from the developer guide.
 Current contract documentation must no longer present the removed APIs as valid.
 
+Completion: updated exported GoDoc, the CLI reference, consumer migration
+guidance, README, integration package documentation, developer guide, internal
+overview, and the unpublished core v0.3.0 note. Current contracts direct callers
+to the invocation reporter and keep operation causes separate from explanations
+and presentation observations. Reviewed the prose against the implementation
+and selected reporting policy; `go doc` checks, local Markdown link and fragment
+checks, and both Markdown whitespace checks pass. Historical integration release
+notes, accepted ADRs, and deferred-work records remain unchanged.
+
 ## Stage 20: Validate the complete end state and finish
 
 Status: pending.