feat(tasks): dependency-aware work graph (blockers, ready, blocking)

The DEPENDS_ON/BLOCKS link types were inert metadata — nothing reasoned about
them. TaskGraph turns them into answerable questions: what a task waits on
(its DEPENDS_ON targets plus any task that BLOCKS it), whether it is ready
(TODO with no unmet blocker — a terminal dependency stops blocking), and what
finishing it would unblock. Readiness surfaces workable tasks to claim; it
never assigns (honouring the rejected /tasks/next scheduler).

Surfaced across the stack:
- TaskService.ready / blockers / blocking.
- Context bundle: a `blocked` flag + `blocked_by` list, rendered as a prominent
  "BLOCKED — waiting on ..." line, so an agent calling task_context learns it
  should wait before charging at the task.
- GET /tasks?ready=true, GET /tasks/{id}/blockers; correx task ready / blockers.

Cross-project dependencies are scoped to a project for now (documented in
TaskGraph). Tests cover both link directions, terminal-dependency clearing,
the ready filter, the reverse blocking direction, the bundle flag, and REST.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/cli/src/main/kotlin/com/correx/apps/cli/commands/TaskCommand.kt

@@ -89,8 +89,10 @@ class TaskCommand : CliktCommand(name = "task") {
     init {
         subcommands(
             TaskListCommand(),
+            TaskReadyCommand(),
             TaskSearchCommand(),
             TaskShowCommand(),
+            TaskBlockersCommand(),
             TaskHistoryCommand(),
             TaskCreateCommand(),
             TaskClaimCommand(),
@@ -133,6 +135,30 @@ class TaskListCommand : TaskHttpCommand("list") {
     }
 }
 
+class TaskReadyCommand : TaskHttpCommand("ready") {
+    private val project by option("--project", help = "Limit to a project")
+
+    override fun run() = http { client ->
+        val query = project?.let { "&project=${enc(it)}" }.orEmpty()
+        val raw = client.get("${baseUrl()}/tasks?ready=true$query").bodyAsText()
+        if (jsonOut()) println(raw) else println(renderTaskList(taskJson.decodeFromString(raw)))
+    }
+}
+
+class TaskBlockersCommand : TaskHttpCommand("blockers") {
+    private val id by argument("TASK_ID")
+
+    override fun run() = http { client ->
+        val resp = client.get("${baseUrl()}/tasks/$id/blockers")
+        if (resp.status == HttpStatusCode.NotFound) {
+            System.err.println("No such task: $id")
+        } else {
+            val raw = resp.bodyAsText()
+            if (jsonOut()) println(raw) else println(renderTaskList(taskJson.decodeFromString(raw)))
+        }
+    }
+}
+
 class TaskSearchCommand : TaskHttpCommand("search") {
     private val query by argument("QUERY", help = "Search text (quote multi-word queries)")
     private val project by option("--project", help = "Limit to a project")