Implement task tree visualization command

Add 'task tree' command to show hierarchical task structure:

Usage:
  task tree # Show all epics with their children task tree <id> #
  Show specific epic/task with children

Features: - Visual status indicators: [ ] open, [~] in-progress,
[✓] done - Shows task type: [Epic] or [Task] - Indented display
for hierarchy - Shows namespace associations

Example output:
  t-PpXWsU [Epic] [ ] Task Manager Improvements [Omni/Task.hs]
    t-PpYZt2 [Task] [ ] Implement child ID generation t-PpZGVf [Task]
    [✓] Add filtering by type and parent

Updated AGENTS.md with usage examples.

Closes task t-PpZlbL

1 files changed, 7 insertions, 0 deletions

diff --git a/Omni/Task.hs b/Omni/Task.hs
index 0aca674..ef912f9 100644
--- a/Omni/Task.hs
+++ b/Omni/Task.hs
@@ -39,6 +39,7 @@ Usage:
   task ready
   task update <id> <status>
   task deps <id>
+  task tree [<id>]
   task export [--flush]
   task import -i <file>
   task test
@@ -51,6 +52,7 @@ Commands:
   ready                         Show ready tasks (not blocked)
   update                        Update task status
   deps                          Show dependency tree
+  tree                          Show task tree (epics with children, or all epics if no ID given)
   export                        Export and consolidate tasks to JSONL
   import                        Import tasks from JSONL file
   test                          Run tests
@@ -158,6 +160,11 @@ move args
   | args `Cli.has` Cli.command "deps" = do
       tid <- getArgText args "id"
       showDependencyTree tid
+  | args `Cli.has` Cli.command "tree" = do
+      maybeId <- case Cli.getArg args (Cli.argument "id") of
+        Nothing -> pure Nothing
+        Just idStr -> pure <| Just (T.pack idStr)
+      showTaskTree maybeId
   | args `Cli.has` Cli.command "export" = do
       exportTasks
       putText "Exported and consolidated tasks to .tasks/tasks.jsonl"