feat(nvim): do/late date chip (+ ↻) on task-view rows (§8)

`:Heph next`/`list` rows now render a compact relative do/late date chip
(today/tomorrow/yesterday/MM-DD/YYYY-MM-DD, mirroring heph-tui's fmt) and
a recurrence ↻, so scheduling is visible at a glance. `<CR>` already jumps
to a row's canonical-context doc. e2e: a do-date-chip render assertion.

Completes the §14 item-2 task-list UX wave.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

heph.nvim/lua/heph/view.lua

@@ -17,9 +17,46 @@ local HINT = "  <CR> open   a add   d done   r refresh"
 
 local ATTENTIONS = { "white", "orange", "red", "blue" }
 
+-- Compact relative date for a do/late epoch-ms value (mirrors heph-tui's fmt):
+-- today / tomorrow / yesterday, MM-DD within the year, else YYYY-MM-DD.
+local function fmt_date(ms)
+  local d = os.date("*t", math.floor(ms / 1000))
+  local n = os.date("*t")
+  local d_noon = os.time({ year = d.year, month = d.month, day = d.day, hour = 12 })
+  local n_noon = os.time({ year = n.year, month = n.month, day = n.day, hour = 12 })
+  local days = math.floor((d_noon - n_noon) / 86400 + 0.5)
+  if days == 0 then
+    return "today"
+  elseif days == 1 then
+    return "tomorrow"
+  elseif days == -1 then
+    return "yesterday"
+  elseif d.year == n.year then
+    return string.format("%02d-%02d", d.month, d.day)
+  else
+    return string.format("%04d-%02d-%02d", d.year, d.month, d.day)
+  end
+end
+
+-- The right-side date chip: a late marker once past due, else the do-date.
+local function date_chip(t)
+  if t.late_on and os.time() * 1000 > t.late_on then
+    return "late:" .. fmt_date(t.late_on)
+  elseif t.do_date then
+    return "do:" .. fmt_date(t.do_date)
+  end
+  return ""
+end
+
 local function row(t)
   local tag = t.attention and ("[" .. t.attention .. "]") or "[ ]"
-  return string.format("%s %s", tag, t.title)
+  local recur = t.recurrence and " ↻" or ""
+  local left = string.format("%s %s%s", tag, t.title, recur)
+  local chip = date_chip(t)
+  if chip ~= "" then
+    return string.format("%-50s %s", left, chip)
+  end
+  return left
 end
 
 local function task_on_line(buf)