fix(parse): skip forge refs in right-to-left metadata scan (#142)

Problem: `parse.body()` scans tokens right-to-left and breaks on the
first non-metadata token. Forge refs like `gl:a/b#12` halted the scan,
preventing metadata tokens to their left (e.g. `due:tomorrow`) from
being parsed. Additionally, `diff.parse_buffer()` ignored
`metadata.priority` from `+!!` tokens and only used checkbox-derived
priority, and priority updates between two non-zero values were silently
skipped.

Solution: Recognize forge ref tokens via `forge.parse_ref()` during the
right-to-left scan and skip past them, re-appending them to the
description so `forge.find_refs()` still works. Prefer
`metadata.priority` over checkbox priority in `parse_buffer()`, and
simplify the priority update condition to catch all value changes.

lua/pending/parse.lua

@@ -1,4 +1,5 @@
 local config = require('pending.config')
+local forge = require('pending.forge')
 
 ---@class pending.Metadata
 ---@field due? string
@@ -543,6 +544,7 @@ function M.body(text)
   local date_pattern_strict = '^' .. vim.pesc(dk) .. ':(%d%d%d%d%-%d%d%-%d%d[T%d:]*)$'
   local date_pattern_any = '^' .. vim.pesc(dk) .. ':(.+)$'
   local rec_pattern = '^' .. vim.pesc(rk) .. ':(%S+)$'
+  local forge_indices = {}
 
   while i >= 1 do
     local token = tokens[i]
@@ -602,6 +604,9 @@ function M.body(text)
               end
               metadata.recur = raw_spec
               i = i - 1
+            elseif forge.parse_ref(token) then
+              table.insert(forge_indices, i)
+              i = i - 1
             else
               break
             end
@@ -615,6 +620,9 @@ function M.body(text)
   for j = 1, i do
     table.insert(desc_tokens, tokens[j])
   end
+  for fi = #forge_indices, 1, -1 do
+    table.insert(desc_tokens, tokens[forge_indices[fi]])
+  end
   local description = table.concat(desc_tokens, ' ')
 
   return description, metadata