feat(buffer): add configurable eol_format for EOL virtual text

Problem: EOL virtual text order (category → recurrence → due) and the
double-space separator are hardcoded in `apply_extmarks()`. Users cannot
reorder, omit, or restyle metadata fields.

Solution: Add `eol_format` config field (default `'%c  %r  %d'`) with
`%c`, `%r`, `%d` specifiers. `parse_eol_format()` tokenizes the format
string; `build_eol_virt()` resolves specifiers against `LineMeta` and
collapses literals around absent fields.

lua/pending/buffer.lua

@@ -352,30 +352,103 @@ function M.get_fold()
   end
 end
 
+---@class pending.EolSegment
+---@field type 'specifier'|'literal'
+---@field key? 'c'|'r'|'d'
+---@field text? string
+
+---@param fmt string
+---@return pending.EolSegment[]
+local function parse_eol_format(fmt)
+  local segments = {}
+  local pos = 1
+  local len = #fmt
+  while pos <= len do
+    if fmt:sub(pos, pos) == '%' and pos + 1 <= len then
+      local key = fmt:sub(pos + 1, pos + 1)
+      if key == 'c' or key == 'r' or key == 'd' then
+        table.insert(segments, { type = 'specifier', key = key })
+        pos = pos + 2
+      else
+        table.insert(segments, { type = 'literal', text = '%' .. key })
+        pos = pos + 2
+      end
+    else
+      local next_pct = fmt:find('%%', pos + 1)
+      local chunk = next_pct and fmt:sub(pos, next_pct - 1) or fmt:sub(pos)
+      table.insert(segments, { type = 'literal', text = chunk })
+      pos = pos + #chunk
+    end
+  end
+  return segments
+end
+
+---@param segments pending.EolSegment[]
+---@param m pending.LineMeta
+---@param icons pending.Icons
+---@return string[][]
+local function build_eol_virt(segments, m, icons)
+  local due_hl = m.overdue and 'PendingOverdue' or 'PendingDue'
+  local resolved = {}
+  for i, seg in ipairs(segments) do
+    if seg.type == 'specifier' then
+      local text, hl
+      if seg.key == 'c' and m.show_category and m.category then
+        text = icons.category .. ' ' .. m.category
+        hl = 'PendingHeader'
+      elseif seg.key == 'r' and m.recur then
+        text = icons.recur .. ' ' .. m.recur
+        hl = 'PendingRecur'
+      elseif seg.key == 'd' and m.due then
+        text = icons.due .. ' ' .. m.due
+        hl = due_hl
+      end
+      resolved[i] = text and { text = text, hl = hl, present = true }
+        or { present = false }
+    else
+      resolved[i] = { text = seg.text, hl = 'Normal', literal = true }
+    end
+  end
+
+  local virt_parts = {}
+  for i, r in ipairs(resolved) do
+    if r.literal then
+      local prev_present, next_present = false, false
+      for j = i - 1, 1, -1 do
+        if not resolved[j].literal then
+          prev_present = resolved[j].present
+          break
+        end
+      end
+      for j = i + 1, #resolved do
+        if not resolved[j].literal then
+          next_present = resolved[j].present
+          break
+        end
+      end
+      if prev_present and next_present then
+        table.insert(virt_parts, { r.text, r.hl })
+      end
+    elseif r.present then
+      table.insert(virt_parts, { r.text, r.hl })
+    end
+  end
+  return virt_parts
+end
+
 ---@param bufnr integer
 ---@param line_meta pending.LineMeta[]
 local function apply_extmarks(bufnr, line_meta)
-  local icons = config.get().icons
+  local cfg = config.get()
+  local icons = cfg.icons
+  local eol_segments = parse_eol_format(cfg.eol_format or '%c  %r  %d')
   vim.api.nvim_buf_clear_namespace(bufnr, ns_eol, 0, -1)
   vim.api.nvim_buf_clear_namespace(bufnr, ns_inline, 0, -1)
   for i, m in ipairs(line_meta) do
     local row = i - 1
     if m.type == 'task' then
-      local due_hl = m.overdue and 'PendingOverdue' or 'PendingDue'
-      local virt_parts = {}
-      if m.show_category and m.category then
-        table.insert(virt_parts, { icons.category .. ' ' .. m.category, 'PendingHeader' })
-      end
-      if m.recur then
-        table.insert(virt_parts, { icons.recur .. ' ' .. m.recur, 'PendingRecur' })
-      end
-      if m.due then
-        table.insert(virt_parts, { icons.due .. ' ' .. m.due, due_hl })
-      end
+      local virt_parts = build_eol_virt(eol_segments, m, icons)
       if #virt_parts > 0 then
-        for p = 1, #virt_parts - 1 do
-          virt_parts[p][1] = virt_parts[p][1] .. '  '
-        end
         vim.api.nvim_buf_set_extmark(bufnr, ns_eol, row, 0, {
           virt_text = virt_parts,
           virt_text_pos = 'eol',