Prepare v0.22.0 release notes and retire completed roadmaps

docs/releases/v0.22.0.md

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+# Promptkit v0.22.0
+
+This minor release adds captured conversation exchanges, optional sequential
+coordination, and explicit execution-group summaries. Applications can continue
+or branch a conversation without reconstructing rendered history, while keeping
+response interpretation and workflow decisions in application code.
+
+## Capture And Continue Conversations
+
+Set `RunRequest.CaptureExchange` to capture a completed run's effective messages
+and final assistant content. Supply its `RunResult.Exchange` as `ContinueFrom`
+on a new request to continue it. Exchanges are reusable, support independent
+branches and different engines, and expose detached history through `Details()`.
+Prepared execution also supports capture of the exact snapshot it executes.
+
+Internal structural-repair instructions and intermediate candidates are not
+conversation history. A completed result with failed structural validation can
+still be captured; an operational error returning no result creates no exchange.
+Follow-ups select their own profiles, output contracts, credentials, and sessions
+under ordinary request rules. See [capture and continuation guidance](../consumers/pkg-promptkit.md#capture-and-continue-a-conversation)
+and the [public exchange contract](../../exchange.go).
+
+## Coordinate Application-Directed Turns
+
+`Engine.Coordinate` advances one conversation branch using an application callback
+and an additional-turn budget. The application selects the next request or stops;
+Promptkit handles turn progression and cancellation. Each completed run releases
+backend admission before the callback, allowing assessment calls to use the same
+backend. Stop and budget exhaustion are control-flow outcomes, not judgments of
+response acceptance. Transport retries and structural repairs remain separate
+from the turn budget.
+
+See the [coordination walkthrough](../consumers/pkg-promptkit.md#coordinate-application-directed-turns)
+and [coordinator GoDoc](../../coordinate.go) for callback and cancellation behavior.
+
+## Collect Selected Execution Facts
+
+`ExecutionGroup` collects explicitly selected execution observations, while
+`ComposeObservers` combines groups with existing diagnostic observers. Detached
+group snapshots report member identities, terminal coverage, attempt/retry/repair
+counts, and available token totals without counting a run more than once.
+Terminal coverage remains distinct from token-usage completeness; membership is
+not inferred from ancestry or nested calls.
+
+See [execution-group guidance](../consumers/pkg-promptkit.md#collect-selected-execution-facts),
+the [group GoDoc](../../execution_group.go), and the updated
+[offline observation example](../../examples/go-library/observe/main.go).
+
+## Efficiency And Compatibility
+
+History assembly and inspection avoid intermediate full-history copies. Observer
+composition retains storage only for selected callbacks and avoids fan-out
+closures for zero or one selected callback.
+
+Capture and coordination are opt-in; existing execution workflows and
+configuration formats need no migration from v0.21.0. The Go consumer minimum
+remains 1.27.0, and dependency versions are unchanged. Exported request, prepared,
+result, and observation structs gained fields; consumers using positional struct
+literals must switch to keyed literals. Continuation metadata adds `parent_run_id`
+to prepared/result JSON when applicable; the opaque exchange itself is excluded.
+Exchanges are in-process capabilities, not serialized restartable sessions.
+
+```sh
+go get go.maximumdirect.net/promptkit@v0.22.0
+```
+
+[COPYRIGHT](https://forge.maximumdirect.net/base-layer/promptkit/src/tag/v0.22.0/COPYRIGHT) | [LICENSE](https://forge.maximumdirect.net/base-layer/promptkit/src/tag/v0.22.0/LICENSE) | [ATTRIBUTION](https://forge.maximumdirect.net/base-layer/promptkit/src/tag/v0.22.0/docs/oss/attribution.md)