docs: update configuration for merge request options and strategies

Co-authored-by: Copilot <copilot@github.com>

Author: obcode

docs/configuration.md

@@ -143,7 +143,6 @@ Patterns are **regular expressions**, so:
 | `description` | GitLab project description | `generated by glabs` | Visible in UI |
 | `accesslevel` | Initial project access (see below) | `developer` | Can be changed later with `setaccess` |
 | `containerRegistry` | Enable container registry | `false` | Auto-enabled if `release.dockerImages` set |
-| `mergeRequest.mergeMethod` | Merge strategy (see below) | `merge` | Applied at project creation |
 | `students` | Override/add assignment-specific students | — | Merged with course-level |
 | `groups` | Override/add assignment-specific groups | — | Merged with course-level |
 
@@ -309,9 +308,29 @@ release:
 | `mergeRequest.pipeline` | Wait for CI | `false` | Require passing checks |
 | `dockerImages` | Images to build | `[]` | Creates container registry entries |
 
-### Merge method values
+**Notes:**
+
+- Container registry is auto-enabled when `dockerImages` is set
+- Enables GitLab Flow workflow for releases
+- Works with CI/CD pipeline to build/deploy
+
+## Merge Request options
+
+Control how merge requests are merged in every generated project:
+
+```yaml
+<assignment>:
+  mergeRequest:
+    mergeMethod: merge    # merge | semi_linear | ff
+```
 
-The assignment-level `mergeRequest.mergeMethod` option controls how merge requests are merged in every generated project:
+### Merge Request keys
+
+| Key | Purpose | Default | Notes |
+|---|---|---|---|
+| `mergeRequest.mergeMethod` | Merge strategy for all MRs | `merge` | Applied at project creation |
+
+### Merge method values
 
 | Value | GitLab UI name | Description |
 |---|---|---|
@@ -327,12 +346,6 @@ blatt01:
     mergeMethod: ff   # Students must keep a linear history
 ```
 
-**Notes:**
-
-- Container registry is auto-enabled when `dockerImages` is set
-- Enables GitLab Flow workflow for releases
-- Works with CI/CD pipeline to build/deploy
-
 ## Full example
 
 ```yaml