refactor: remove redundant area: prefix from comment-on-work-item target field

The target field type system already disambiguates naturally:
- number → single work item ID
- array of numbers → list of IDs
- "*" → wildcard
- any other string → area path prefix

The area: prefix was unnecessary since no other string variant
could collide with area paths.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jamesadevine

AGENTS.md

@@ -774,14 +774,14 @@ Adds a comment to an existing Azure DevOps work item. This is the ADO equivalent
   - `"*"` - Any work item in the project (unrestricted, must be explicit)
   - `12345` - A specific work item ID
   - `[12345, 67890]` - A list of allowed work item IDs
-  - `"area:Some\\Path"` - Work items under the specified area path prefix (validated via ADO API at Stage 2)
+  - `"Some\\Path"` - Work items under the specified area path prefix (any string that isn't `"*"`, validated via ADO API at Stage 2)
 
 **Example configuration:**
 ```yaml
 safe-outputs:
   comment-on-work-item:
     max: 3
-    target: "area:4x4\\QED"
+    target: "4x4\\QED"
 ```
 
 **Note:** The `target` field is required. If omitted, compilation fails with an error. This ensures operators are intentional about which work items agents can comment on.

src/compile/common.rs

@@ -595,7 +595,7 @@ pub fn validate_comment_target(front_matter: &FrontMatter) -> Result<()> {
                      target: \"*\"           # any work item (unrestricted)\n  \
                      target: 12345          # specific work item ID\n  \
                      target: [12345, 67890] # list of work item IDs\n  \
-                     target: \"area:Path\"   # work items under area path prefix\n"
+                     target: \"Path\\\\Sub\"   # work items under area path prefix\n"
                 );
             }
         } else {

src/tools/comment_on_work_item.rs

@@ -48,18 +48,18 @@ impl Sanitize for CommentOnWorkItemResult {
 /// Target scope for which work items can be commented on.
 ///
 /// Deserialized from the `target` field in front matter:
-/// - `"*"` → `Wildcard` (any work item)
-/// - `12345` → `Id(12345)` (single work item)
-/// - `[12345, 67890]` → `Ids(vec![12345, 67890])` (set of work items)
-/// - `"area:Some\\Path"` → `AreaPath("Some\\Path")` (work items under area path prefix)
+/// - `"*"` → wildcard (any work item)
+/// - `12345` → single work item ID
+/// - `[12345, 67890]` → set of work item IDs
+/// - `"Some\\Path"` → area path prefix (any string that isn't `"*"`)
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(untagged)]
 pub enum CommentTarget {
     /// A single work item ID
     SingleId(i64),
     /// A list of work item IDs
     IdList(Vec<i64>),
-    /// A string target: "*" for wildcard, "area:..." for area path
+    /// A string target: "*" for wildcard, anything else is an area path
     StringTarget(String),
 }
 
@@ -78,7 +78,7 @@ impl CommentTarget {
     /// Get the area path prefix if this is an area-path target.
     pub fn area_path_prefix(&self) -> Option<&str> {
         match self {
-            CommentTarget::StringTarget(s) if s.starts_with("area:") => Some(&s[5..]),
+            CommentTarget::StringTarget(s) if s != "*" => Some(s.as_str()),
             _ => None,
         }
     }
@@ -433,7 +433,7 @@ target: "*"
     #[test]
     fn test_config_area_path_target() {
         let yaml = r#"
-target: "area:4x4\\QED"
+target: "4x4\\QED"
 "#;
         let config: CommentOnWorkItemConfig = serde_yaml::from_str(yaml).unwrap();
         assert!(config.target.allows_id(1).is_none());