fix(parse): position-independent inline metadata parsing (#164)

Problem: `parse.body()` scanned tokens right-to-left and broke on the
first non-metadata token, so metadata only worked at the trailing end
of a line. `due:tomorrow Fix the bug` silently failed to parse the
due date.

Solution: Replace the right-to-left `while` loop with a single
left-to-right pass that extracts metadata tokens from any position.
Duplicate metadata tokens are dropped with a `log.warn`. Update docs
and tests accordingly.

doc/pending.txt

@@ -664,7 +664,7 @@ On `:w`, the description becomes `Buy milk`, the due date is stored as
 placed under the `Errands` category header.
 
 Only the first occurrence of each metadata type is consumed — duplicate
-tokens are silently dropped.
+tokens are dropped with a warning.
 
 Omnifunc completion is available for `due:`, `cat:`, and `rec:` token types.
 In insert mode, type the token prefix and press `<C-x><C-o>` to see

lua/pending/parse.lua

@@ -1,5 +1,6 @@
 local config = require('pending.config')
 local forge = require('pending.forge')
+local log = require('pending.log')
 
 ---@class pending.Metadata
 ---@field due? string
@@ -553,6 +554,8 @@ function M.body(text)
     if due_val and is_valid_datetime(due_val) then
       if not metadata.due then
         metadata.due = due_val
+      else
+        log.warn('duplicate ' .. dk .. ': token ignored: ' .. token)
       end
       consumed = true
     end
@@ -563,6 +566,8 @@ function M.body(text)
         if resolved then
           if not metadata.due then
             metadata.due = resolved
+          else
+            log.warn('duplicate ' .. dk .. ': token ignored: ' .. token)
           end
           consumed = true
         end
@@ -574,6 +579,8 @@ function M.body(text)
       if cat_val then
         if not metadata.category then
           metadata.category = cat_val
+        else
+          log.warn('duplicate ' .. ck .. ': token ignored: ' .. token)
         end
         consumed = true
       end
@@ -585,6 +592,8 @@ function M.body(text)
         if not metadata.priority then
           local max = config.get().max_priority or 3
           metadata.priority = math.min(#pri_bangs, max)
+        else
+          log.warn('duplicate priority token ignored: ' .. token)
         end
         consumed = true
       end
@@ -602,6 +611,8 @@ function M.body(text)
           if not metadata.recur then
             metadata.recur_mode = rec_val:sub(1, 1) == '!' and 'completion' or nil
             metadata.recur = raw_spec
+          else
+            log.warn('duplicate ' .. rk .. ': token ignored: ' .. token)
           end
           consumed = true
         end

spec/parse_spec.lua

@@ -48,16 +48,35 @@ describe('parse', function()
       assert.are.equal('Errands', meta.category)
     end)
 
-    it('first occurrence wins for duplicate keys', function()
+    it('first occurrence wins for duplicate keys and warns', function()
+      local warnings = {}
+      local orig = vim.notify
+      vim.notify = function(m, level)
+        if level == vim.log.levels.WARN then
+          table.insert(warnings, m)
+        end
+      end
       local desc, meta = parse.body('Buy milk due:2026-03-15 due:2026-04-01')
+      vim.notify = orig
       assert.are.equal('Buy milk', desc)
       assert.are.equal('2026-03-15', meta.due)
+      assert.are.equal(1, #warnings)
+      assert.truthy(warnings[1]:find('duplicate', 1, true))
     end)
 
-    it('drops identical duplicate metadata tokens', function()
+    it('drops identical duplicate metadata tokens and warns', function()
+      local warnings = {}
+      local orig = vim.notify
+      vim.notify = function(m, level)
+        if level == vim.log.levels.WARN then
+          table.insert(warnings, m)
+        end
+      end
       local desc, meta = parse.body('Buy milk due:tomorrow due:tomorrow')
+      vim.notify = orig
       assert.are.equal('Buy milk', desc)
       assert.are.equal(os.date('%Y-%m-%d', os.time() + 86400), meta.due)
+      assert.are.equal(1, #warnings)
     end)
 
     it('stops at non-meta token', function()