fix: more work on background tasks

specs/generation.allium

@@ -44,9 +44,10 @@ surface GenerationRuntimeSurface {
         -- "Generated" for a full render and "Rewrote" for a validation apply —
         -- and advances the bar by the number of URLs written.
         --
-        -- Before section work begins, generation counts its planned URLs. The
-        -- task reports 0/total immediately and advances once per rendered URL,
-        -- matching bDS2's route-based generation progress.
+        -- Route preparation and counting happen in background work before
+        -- section rendering. Validation totals count only prepared URLs
+        -- selected by the validation report, not the whole section. The task
+        -- reports 0/total immediately and advances once per rendered URL.
         --
         -- Full generation and validation apply share the same structuring: a
         -- task group containing one task per section (Render Site Core, Render
@@ -310,6 +311,9 @@ rule ApplyValidation {
     -- unchanged post route refreshes its tracked generation time so the
     -- automatic follow-up validation does not report it stale again.
     ensures: GenerateSiteRequested(plan_generation(project_id, sections))
+    -- Observable phases are prepare, affected render sections, optional
+    -- calendar regeneration, search indexing, and final validation. Failure or
+    -- cancellation stops every dependent phase.
 }
 
 -- Day-block grouping for archives

specs/layout.allium

@@ -262,7 +262,9 @@ invariant PanelTabFallback {
     -- git_log unavailable when neither post nor media tab is active
 }
 
--- Tasks tab: last 10 tasks, newest first, with progress/cancel.
+-- Tasks tab: every active task plus the 10 newest finished tasks, with
+-- progress/cancel. Active groups always include every child needed to show a
+-- complete group even when this exceeds the finished-history limit.
 --   Tasks with shared group_id are collapsible groups showing bDS2-style
 --   average child progress; pending children contribute zero.
 -- Output tab: log entries with copy-all button.
@@ -287,6 +289,12 @@ value StatusBarLeft {
     running_task_overflow: Integer?     -- "+N more" count when multiple running
 }
 
+invariant StatusBarTaskSelection {
+    -- The indicator selects the first running task, otherwise the first
+    -- pending task. Overflow counts every other running or pending task.
+    -- Status remains typed until its display label is localized.
+}
+
 value StatusBarRight {
     -- In display order (left to right):
     post_status: String?                -- draft|published|archived dot, when post tab active

specs/script.allium

@@ -135,6 +135,11 @@ surface ScriptRuntimeSurface {
         -- sync_from_posts.
         -- bds.tasks: get, status_snapshot, cancel, get_all, get_running,
         -- clear_completed.
+        -- get and get_all inspect every retained task rather than the
+        -- status-snapshot history cap; get_all is newest first. get_running
+        -- contains only running tasks. cancel succeeds only for a pending or
+        -- running task. clear_completed removes completed tasks while keeping
+        -- failed and cancelled results.
         -- bds.sync: check_availability, get_repo_state, get_status,
         -- get_history, get_remote_state, fetch, pull, push, commit_all.
         -- bds.publish: upload_site.

specs/task.allium

@@ -6,6 +6,9 @@
 entity Task {
     name: String
     status: pending | running | completed | failed | cancelled
+    source: local | remote
+    cancellable: Boolean
+    cancellation_requested: Boolean
     progress: Decimal?              -- 0.0..1.0
     message: String?
     group_id: String?               -- Optional task grouping
@@ -28,6 +31,7 @@ surface TaskControlSurface {
         SubmitTaskRequested(name, work)
         CancelTaskRequested(task)
         RegisterExternalTaskRequested(name)
+        TaskStateRequested()
 }
 
 surface TaskRuntimeSurface {
@@ -38,6 +42,8 @@ surface TaskRuntimeSurface {
         TaskWorkFailed(task, error_message)
         ProgressReported(task, value, message)
         FinishedTaskEvictionDue()
+        WorkerCapacityAvailable()
+        TaskWorkStopped(task)
 }
 
 surface TaskSurface {
@@ -46,6 +52,7 @@ surface TaskSurface {
     exposes:
         task.name
         task.status
+        task.source
         task.progress when task.progress != null
         task.message when task.message != null
         task.group_id when task.group_id != null
@@ -74,13 +81,23 @@ invariant FifoQueue {
 
 rule SubmitTask {
     when: SubmitTaskRequested(name, work)
-    let running_tasks = Tasks where status = running
     ensures:
-        let task = Task.created(name: name, status: pending)
+        let task = Task.created(
+            name: name,
+            status: pending,
+            source: local,
+            cancellable: true,
+            cancellation_requested: false
+        )
         task.status = pending
-        if running_tasks.count < config.max_concurrent:
-            task.status = running
-            TaskStarted(task, work)
+}
+
+rule StartNextTask {
+    when: WorkerCapacityAvailable()
+    let pending_tasks = Tasks where status = pending
+    requires: pending_tasks.count > 0
+    ensures: pending_tasks.first.status = running
+    ensures: TaskStarted(pending_tasks.first)
 }
 
 rule CompleteTask {
@@ -99,8 +116,28 @@ rule FailTask {
 
 rule CancelTask {
     when: CancelTaskRequested(task)
-    requires: task.status = running or task.status = pending
-    -- Cancellation uses a runtime-specific cancellation mechanism
+    requires: task.status = pending
+    ensures: task.status = cancelled
+    ensures: NextQueuedTaskStarted()
+}
+
+rule RequestRunningTaskCancellation {
+    when: CancelTaskRequested(task)
+    requires: task.status = running
+    requires: task.cancellable
+    ensures: task.cancellation_requested = true
+    ensures: StopTaskWorkRequested(task)
+    @guidance
+        -- Long operations observe the request at phase or item boundaries.
+        -- Owned child processes are terminated when the platform permits it.
+        -- The task remains running and occupies its worker slot until work
+        -- actually stops; status surfaces expose cancellation_requested.
+}
+
+rule FinishRunningTaskCancellation {
+    when: TaskWorkStopped(task)
+    requires: task.status = running
+    requires: task.cancellation_requested
     ensures: task.status = cancelled
     ensures: NextQueuedTaskStarted()
 }
@@ -110,6 +147,9 @@ rule ReportProgress {
     -- Progress events throttled to 250ms
     ensures: task.progress = value
     ensures: task.message = message
+    @guidance
+        -- A report whose value is 1.0 is always accepted so the terminal
+        -- localized phase text cannot be dropped by throttling.
 }
 
 invariant ProgressThrottled {
@@ -139,11 +179,24 @@ rule EvictFinishedTasks {
             ensures: not exists task
 }
 
+rule PruneFinishedTasksOnAccess {
+    when: TaskStateRequested()
+    for task in Tasks where status in {completed, failed, cancelled}:
+        if now - task.finished_at >= config.finished_task_ttl:
+            ensures: not exists task
+}
+
 -- External tasks: lifecycle controlled by caller (e.g., renderer-side scripts)
 rule RegisterExternalTask {
     when: RegisterExternalTaskRequested(name)
     ensures:
-        let task = Task.created(name: name, status: running)
+        let task = Task.created(
+            name: name,
+            status: running,
+            source: remote,
+            cancellable: true,
+            cancellation_requested: false
+        )
         task.status = running
     @guidance
         -- External tasks are not managed by the queue