chore: source formatting and spec allignment

RUST_PLAN_CORE.md

@@ -757,6 +757,8 @@ By Wave 3, bds-editor must support the full feature set documented in the editor
 - preview server binds to `127.0.0.1:4123` (localhost only, fixed port)
 - preview and generated HTML use local assets only
 - preview must support drafts and language-prefixed routes
+- each post editor can switch between Markdown and an internal Wry preview panel backed by the draft preview route
+- Open in Browser starts or reuses the same preview server and opens its URL in the external system browser; it does not replace the internal panel
 - rendered language is controlled by project settings, not by UI locale
 
 ### One-shot AI operations
@@ -792,12 +794,13 @@ Wave 4 introduces the one-shot AI client in `bds-core`. This is a minimal `reqwe
 
 - fixture-based generation comparisons against current app output
 - preview route tests for posts, drafts, assets, media, and language routes
+- UI tests for switching a post between Markdown and internal preview, plus the external Open in Browser command
 - template compatibility tests using current `.liquid` templates
 
 ### Done when
 
 - the same project can be generated by both apps with matching output
-- preview is accurate enough to be trusted as an authoring tool
+- internal and external preview are accurate enough to be trusted as authoring tools
 - milestone M4 acceptance review passes
 
 ## Wave 5: Publishing And Operational Integrity
@@ -920,4 +923,4 @@ Cross-platform packaging is not core scope, but the architecture does not accumu
 ## Supporting Docs
 
 - [RUST_EXECUTION_BACKLOG.md](RUST_EXECUTION_BACKLOG.md)
-- [RUST_COMPATIBILITY_MATRIX_TEMPLATE.md](RUST_COMPATIBILITY_MATRIX_TEMPLATE.md)
+- [RUST_COMPATIBILITY_MATRIX_TEMPLATE.md](RUST_COMPATIBILITY_MATRIX_TEMPLATE.md)