feat: TUI tags panels (cloud, manage, merge) wired to the shared tags backend (issue #34)

specs/tui.allium

@@ -134,6 +134,26 @@ rule SettingsPanel {
     ensures: SettingsFormShownEditedOrSaved()
 }
 
+rule TagsPanel {
+    when: TuiKeyPressed(code: "5")
+    -- "5" opens the tags view (issue #34), matching the GUI panel
+    -- numbering. The sidebar lists the same three sections as the GUI
+    -- tags editor (Tag Cloud, Create / Edit, Merge Tags — from
+    -- BDS.UI.Sidebar's tags nav view); enter opens the section in the
+    -- main area, all backed by BDS.UI.TagsPanel over the same BDS.Tags
+    -- operations as the GUI editor. Cloud lists tags with their post
+    -- usage counts ordered by usage; manage is alphabetical with "n"
+    -- (create prompt), enter (rename prompt), "c" (cycle colour through
+    -- the shared presets), "t" (cycle post template), "d" then "y"
+    -- (delete with post-count confirmation; any other key cancels) and
+    -- "s" (sync tags from post tags); merge marks tags with space and
+    -- "m" merges the marked tags into the selected one (at least two,
+    -- target included). Text prompts live in the status line; esc
+    -- cancels the prompt, then closes the panel. Domain tag events
+    -- reload an open panel, keeping it in sync with GUI and CLI writes.
+    ensures: TagsPanelShownOrEdited()
+}
+
 rule GitPanel {
     when: TuiKeyPressed(code: "7")
     -- "7" opens the git panel (issue #30) for content sync: the sidebar