docs: roll over per-crate changelogs for 1.0.0-rc.4 (#320)

Author: StefanSteiner

hyperdb-api/CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+## [1.0.0-rc.4] - 2026-09-08
+
 ### Fixed
 
 - **IPC transport: a process that spawns several IPC `HyperProcess` instances

hyperdb-mcp/CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+## [1.0.0-rc.4] - 2026-09-08
+
 ### Changed
 
 - **The daemon now connects to its `hyperd` engine over a local IPC channel