feat(tasks): TUI task board

Add a cross-project task board to the TUI (T / palette): a roster fetched
from GET /tasks with vim-style nav, refresh, and an enter-to-open detail
pane (goal, criteria, paths, links, notes) built from the list payload — no
extra fetch. Server: TaskService.listAll() and a project-optional GET /tasks
(scoped with ?project=, whole board without; recent-first).

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

core/tasks/src/main/kotlin/com/correx/core/tasks/TaskService.kt

@@ -55,6 +55,16 @@ class TaskService(
     fun list(projectId: ProjectId): List<Task> =
         board(projectId).filterValues { !it.deleted }.map { (id, state) -> Task(id, state) }
 
+    /**
+     * Every task across every project, for a cross-project board. Enumerates the per-project task
+     * streams ([TaskStreams.PREFIX]) and rebuilds each — there is no global task stream, so this is
+     * the union of the per-project boards.
+     */
+    fun listAll(): List<Task> =
+        eventStore.allSessionIds()
+            .filter { it.value.startsWith(TaskStreams.PREFIX) }
+            .flatMap { stream -> list(ProjectId(stream.value.removePrefix(TaskStreams.PREFIX))) }
+
     fun getTask(taskId: TaskId): Task? {
         val state = board(projectOf(taskId))[taskId] ?: return null
         return if (state.deleted) null else Task(taskId, state)

core/tasks/src/test/kotlin/com/correx/core/tasks/TaskServiceTest.kt

@@ -72,6 +72,14 @@ class TaskServiceTest {
         assertNull(service.claim(TaskId("auth-999"), "claude-opus"))
     }
 
+    @Test
+    fun `listAll spans every project's stream`() = runBlocking {
+        service.createTask(project, "a", "g")
+        service.createTask(ProjectId("billing"), "b", "g")
+
+        assertEquals(setOf("auth-1", "billing-1"), service.listAll().map { it.taskId.value }.toSet())
+    }
+
     @Test
     fun `keys keep incrementing even after deletion`() = runBlocking {
         val first = service.createTask(project, "one", "g").taskId