feat(KB-341): unify steeringComments and comments into single comments system

- Consolidate steeringComments and comments into unified comments field using TaskComment type

- Remove SteeringComment type, migrate all comments to TaskComment format

- Update addComment to delegate to addTaskComment with auto-refinement for done tasks

- Merge legacy steeringComments data into comments during database migration

- Update dashboard API endpoint from /steer to /comments

- Update executor to use unified comments field for real-time injection

- Update PR comment handler to use addTaskComment method

.changeset/unify-comments.md

@@ -2,4 +2,21 @@
 "@gsxdsm/fusion": minor
 ---
 
-Unify steeringComments and comments into a single comments field. All comments are now injected into the AI execution context.
+Unify task comments into a single system
+
+The task comment system has been consolidated from two separate systems (`steeringComments` and `comments`) into a single unified `comments` field using the `TaskComment` type. This simplifies the API and removes confusion about which comment type to use.
+
+**Breaking Changes:**
+- Removed `SteeringComment` type (use `TaskComment` instead)
+- Removed `steeringComments` field from `Task` interface
+- All comments are now stored in the unified `comments` field
+- The `/api/tasks/:id/steer` endpoint still works but now uses the unified comment system internally
+
+**Migration:**
+- Legacy `steeringComments` data is automatically merged into `comments` during database read operations
+- The `addSteeringComment` method now delegates to `addTaskComment` while preserving auto-refinement behavior for done tasks
+
+**UI Changes:**
+- "Steering Comments" tab heading changed to "Comments"
+- Placeholder text changed from "Add a steering comment..." to "Add a comment..."
+- Button text changed from "Add Steering Comment" to "Add Comment"