feat: trigger forge refresh on buffer open

Problem: forge metadata was never fetched, so virt text highlights
could not reflect remote issue/PR state.

Solution: call `forge.refresh()` in `M.open()` so metadata is
fetched once per `:Pending` invocation rather than on every render.

lua/pending/init.lua

@@ -189,6 +189,8 @@ function M.open()
   local bufnr = buffer.open()
   M._setup_autocmds(bufnr)
   M._setup_buf_mappings(bufnr)
+  local forge = require('pending.forge')
+  forge.refresh(s)
   return bufnr
 end
 
@@ -1451,6 +1453,7 @@ function M.command(args)
   end
 end
 
+
 ---@return string[]
 function M.sync_backends()
   return (discover_backends())