0.8.2: Counting House → Exchange + fix click-doesn't-refresh-detail bug

Rename
------
Counting House → Exchange everywhere. "Exchange" reads as intuitive
("an exchange where I trade items for spurs") where Counting House
was historically accurate but obscure. /bns open counthouse →
/bns open exchange. Class CountingHouseScreen → ExchangeScreen.
Lang key counting_house → exchange. NPC name suggestion in docs:
"Exchange Clerk".

Click-doesn't-refresh bug
-------------------------
ItemCell/BountyRow/PlotRow's mousePressed updated the static
`selected` field, but the detail sub-panel was already built with
the old value at refreshWidgets time. Result: clicking a different
item updated the highlight but the right-side detail pane never
changed.

Fix: call getGui().refreshWidgets() after updating selection. FTB
Library's recursive refresh re-runs SellDetail.addWidgets/
BountyDetail.addWidgets/PlotDetail.addWidgets with the new selected
value. Standard FTB Library pattern for "selection changed → redraw".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

gradle.properties

@@ -19,5 +19,5 @@ loader_version_range=[1,)
 mod_id=bnstoolkit
 mod_name=Brass and Sigil Toolkit
 mod_license=All Rights Reserved
-mod_version=0.8.1
+mod_version=0.8.2
 mod_group_id=uk.sijbers.bnstoolkit