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/server/src/main/kotlin/com/correx/apps/server/routes/TaskRoutes.kt

@@ -126,6 +126,12 @@ fun Route.taskRoutes(module: ServerModule) {
 
 private fun Route.taskCollectionRoutes(service: TaskService) {
     get {
+        // ?ready=true short-circuits to the dependency-aware workable set (TODO, no unmet blockers).
+        if (call.request.queryParameters["ready"]?.toBoolean() == true) {
+            val readyProject = call.request.queryParameters["project"]
+            val workable = service.ready(readyProject?.let { ProjectId(it) })
+            return@get call.respond(workable.map { it.toResponse() })
+        }
         val statusRaw = call.request.queryParameters["status"]
         val statusFilter = statusRaw?.let {
             parseEnum<TaskStatus>(it) ?: return@get call.respond(HttpStatusCode.BadRequest, "Invalid status: $it")
@@ -209,6 +215,12 @@ private fun Route.taskCrudRoutes(service: TaskService, assembler: TaskContextAss
         if (events.isEmpty()) return@get call.respond(HttpStatusCode.NotFound, "Task not found")
         call.respondText(TaskHistory.render(events), ContentType.Text.Plain)
     }
+    // Unfinished tasks this one is waiting on (its dependencies + inbound blocks).
+    get("/blockers") {
+        val id = taskId() ?: return@get call.respond(HttpStatusCode.BadRequest, "Missing task id")
+        if (service.getTask(id) == null) return@get call.respond(HttpStatusCode.NotFound, "Task not found")
+        call.respond(service.blockers(id).map { it.toResponse() })
+    }
 }
 
 private fun Route.taskTransitionRoutes(service: TaskService) {

apps/server/src/test/kotlin/com/correx/apps/server/routes/TaskRoutesTest.kt

@@ -256,6 +256,35 @@ class TaskRoutesTest {
         }
     }
 
+    @Test
+    fun `ready returns unblocked TODO tasks and blockers explains a wait`(@TempDir tempDir: Path) {
+        testApplication {
+            application { configureServer(buildModule(tempDir)) }
+            val client = createClient {}
+            client.createTask() // demo-1, TODO
+            client.post("/tasks") {
+                contentType(ContentType.Application.Json)
+                setBody("""{"project":"demo","title":"second","goal":"g"}""")
+            }
+            // demo-2 depends on demo-1 (id infers to a TASK target).
+            client.post("/tasks/demo-2/links") {
+                contentType(ContentType.Application.Json)
+                setBody("""{"targetId":"demo-1","type":"DEPENDS_ON"}""")
+            }
+
+            val ready = client.get("/tasks?ready=true")
+            assertEquals(HttpStatusCode.OK, ready.status)
+            val rows = testJson.parseToJsonElement(ready.bodyAsText()) as JsonArray
+            assertEquals(1, rows.size)
+            assertEquals("demo-1", (rows[0] as JsonObject)["id"]!!.jsonPrimitive.content)
+
+            val blockers = client.get("/tasks/demo-2/blockers")
+            assertEquals(HttpStatusCode.OK, blockers.status)
+            val blk = testJson.parseToJsonElement(blockers.bodyAsText()) as JsonArray
+            assertEquals("demo-1", (blk.single() as JsonObject)["id"]!!.jsonPrimitive.content)
+        }
+    }
+
     @Test
     fun `GET history renders the lifecycle timeline`(@TempDir tempDir: Path) {
         testApplication {