refactor(forge): rename auto_close to close

Problem: `auto_close` is verbose given it's already namespaced under
`forge.` in the config table.

Solution: Rename to `close` in config defaults, class annotation,
`refresh()` usage, and vimdoc.

doc/pending.txt

@@ -1500,7 +1500,7 @@ Configuration: ~
 >lua
     vim.g.pending = {
       forge = {
-        auto_close = false,
+        close = false,
         warn_missing_cli = true,
         github = {
           icon = '',
@@ -1522,7 +1522,7 @@ Configuration: ~
 <
 
 Top-level fields: ~
-    {auto_close}        (boolean, default: false) When true, tasks linked to
+    {close}        (boolean, default: false) When true, tasks linked to
                         closed/merged remote issues are automatically marked
                         done on buffer open.
     {warn_missing_cli}  (boolean, default: true) When true, warns once per
@@ -1550,7 +1550,7 @@ than 5 minutes are re-fetched asynchronously. The buffer renders immediately
 with cached data and updates extmarks when the fetch completes.
 
 State pull: ~
-Requires `forge.auto_close = true`. After fetching, if the remote issue/PR
+Requires `forge.close = true`. After fetching, if the remote issue/PR
 is closed or merged and the local task is pending/wip/blocked, the task is
 automatically marked as done. Disabled by default. One-way: local status
 changes do not push back to the forge.

lua/pending/config.lua

@@ -40,7 +40,7 @@
 ---@field shorthand? string
 
 ---@class pending.ForgeConfig
----@field auto_close? boolean
+---@field close? boolean
 ---@field warn_missing_cli? boolean
 ---@field [string] pending.ForgeInstanceConfig
 
@@ -154,7 +154,7 @@ local defaults = {
   },
   sync = {},
   forge = {
-    auto_close = false,
+    close = false,
     warn_missing_cli = true,
     github = {
       icon = '',

lua/pending/forge.lua

@@ -310,7 +310,7 @@ function M.refresh(s)
           any_fetched = true
           local forge_cfg = config.get().forge or {}
           if
-            forge_cfg.auto_close
+            forge_cfg.close
             and (cache.state == 'closed' or cache.state == 'merged')
             and (task.status == 'pending' or task.status == 'wip' or task.status == 'blocked')
           then