feat(store): add recur and recur_mode task fields

Problem: the task schema has no fields for storing recurrence rules.

Solution: add recur and recur_mode to the Task class, known_fields,
task_to_table, table_to_task, and the add() signature.

lua/pending/store.lua

@@ -7,6 +7,8 @@ local config = require('pending.config')
 ---@field category? string
 ---@field priority integer
 ---@field due? string
+---@field recur? string
+---@field recur_mode? 'scheduled'|'completion'
 ---@field entry string
 ---@field modified string
 ---@field end? string
@@ -56,6 +58,8 @@ local known_fields = {
   category = true,
   priority = true,
   due = true,
+  recur = true,
+  recur_mode = true,
   entry = true,
   modified = true,
   ['end'] = true,
@@ -81,6 +85,12 @@ local function task_to_table(task)
   if task.due then
     t.due = task.due
   end
+  if task.recur then
+    t.recur = task.recur
+  end
+  if task.recur_mode then
+    t.recur_mode = task.recur_mode
+  end
   if task['end'] then
     t['end'] = task['end']
   end
@@ -105,6 +115,8 @@ local function table_to_task(t)
     category = t.category,
     priority = t.priority or 0,
     due = t.due,
+    recur = t.recur,
+    recur_mode = t.recur_mode,
     entry = t.entry,
     modified = t.modified,
     ['end'] = t['end'],
@@ -224,7 +236,7 @@ function M.get(id)
   return nil
 end
 
----@param fields { description: string, status?: string, category?: string, priority?: integer, due?: string, order?: integer, _extra?: table }
+---@param fields { description: string, status?: string, category?: string, priority?: integer, due?: string, recur?: string, recur_mode?: string, order?: integer, _extra?: table }
 ---@return pending.Task
 function M.add(fields)
   local data = M.data()
@@ -236,6 +248,8 @@ function M.add(fields)
     category = fields.category or config.get().default_category,
     priority = fields.priority or 0,
     due = fields.due,
+    recur = fields.recur,
+    recur_mode = fields.recur_mode,
     entry = now,
     modified = now,
     ['end'] = nil,

spec/store_spec.lua

@@ -196,6 +196,41 @@ describe('store', function()
     end)
   end)
 
+  describe('recurrence fields', function()
+    it('persists recur and recur_mode through round-trip', function()
+      store.load()
+      store.add({ description = 'Recurring', recur = 'weekly', recur_mode = 'scheduled' })
+      store.save()
+      store.unload()
+      store.load()
+      local task = store.get(1)
+      assert.are.equal('weekly', task.recur)
+      assert.are.equal('scheduled', task.recur_mode)
+    end)
+
+    it('persists recur without recur_mode', function()
+      store.load()
+      store.add({ description = 'Simple recur', recur = 'daily' })
+      store.save()
+      store.unload()
+      store.load()
+      local task = store.get(1)
+      assert.are.equal('daily', task.recur)
+      assert.is_nil(task.recur_mode)
+    end)
+
+    it('omits recur fields when not set', function()
+      store.load()
+      store.add({ description = 'No recur' })
+      store.save()
+      store.unload()
+      store.load()
+      local task = store.get(1)
+      assert.is_nil(task.recur)
+      assert.is_nil(task.recur_mode)
+    end)
+  end)
+
   describe('active_tasks', function()
     it('excludes deleted tasks', function()
       store.load()