docs: Fix composefs storage paths

Correct the state directory path from the incorrect
/var/lib/bootc/composefs-backend/ to the actual /sysroot/state/deploy
as defined in composefs_consts.rs. Also clarify that transient state
is stored in /run/composefs.

Signed-off-by: Ona <[email protected]>

Co-authored-by: Ona <[email protected]>

Author: cgwalters-bot

docs/todo/composefs.md

@@ -34,10 +34,7 @@ bootc/
 
 ### Storage Model
 
-- **Composefs objects**: Stored in repository with fsverity support
-- **State directory**: `/var/lib/bootc/composefs-backend/` (transient state in `/run`)
-- **Boot entries**: BLS configs or UKI with composefs= kernel parameter
-- **Image metadata**: Stored with deployment state including target imgref
+The composefs backend uses a different storage model than the traditional ostree approach. Composefs objects are stored in the repository with optional fsverity support. The state directory is located at `/sysroot/state/deploy`, with transient state (such as staged deployments) stored in `/run/composefs`. Boot entries are either BLS configs or UKI with the `composefs=` kernel parameter. Image metadata is stored with the deployment state, including the target image reference.
 
 ## Remaining Work