test: add e2e test suite and fix namespace/mention/assignee flags

README.md

@@ -157,6 +157,7 @@ Relations connect nodes together:
 | `subtask` | issue → issue | Shows as tree under parent |
 | `related` | any ↔ any | Shown in related section |
 | `assignee` | issue → user | Adds to user's inbox |
+| `in_namespace`| any → namespace | Groups nodes by project or team |
 
 ```bash
 # Create subtask
@@ -189,7 +190,6 @@ ax add "Task" --type issue --status open --prio high
 | `_type` | `issue`, `note`, `user`, `namespace` | Yes (default: `issue`) |
 | `_status` | `open`, `done` | No |
 | `_prio` | `high`, `medium`, `low` | No |
-| `_namespace` | any string | Yes (default: current user) |
 
 ## Mentions and Inbox