feat(merge): toggle add/remove per side, MAIN/INCOMING labels, files readout

- Conflict accept is now a per-side toggle: > adds MAIN (ours), < adds INCOMING
  (theirs) in click order (first on top); clicking again removes that side, so each
  side is included at most once. Region content is rebuilt from the included set.
- Drop the separate reset (x) control — toggling both off clears the region.
- Relabel the panes/tooltips Ours/Theirs -> MAIN/INCOMING (merge target vs task).
- Add a cross-file 'N of M files unresolved' readout (FilesSummary) so you can see
  how many more files still have conflicts. en/de updated; Ui 128 + Loc 16 green.

src/ClaudeDo.Localization/locales/de.json

@@ -400,15 +400,16 @@
     "windowTitle": "Merge-Konflikte lösen",
     "modalTitle": "KONFLIKTE LÖSEN",
     "loading": "Konflikte werden geladen…",
-    "ours": "OURS · aktuell (Ziel-Branch)",
+    "ours": "MAIN · Ziel-Branch",
     "result": "ERGEBNIS",
-    "theirs": "THEIRS · eingehend (Task)",
+    "theirs": "INCOMING · Task-Branch",
     "binaryHint": "Binärdateien können hier nicht zusammengeführt werden — brich ab und löse sie in deinem Editor:",
     "prevConflict": "Vorheriger Konflikt (Umschalt+F8)",
     "nextConflict": "Nächster Konflikt (F8)",
-    "acceptOurs": "Ours hinzufügen (Reihenfolge = Stapel)",
-    "acceptTheirs": "Theirs hinzufügen (Reihenfolge = Stapel)",
-    "clearConflict": "Konflikt zurücksetzen (neu beginnen)",
+    "acceptOurs": "Main hinzufügen",
+    "acceptTheirs": "Incoming hinzufügen",
+    "removeOurs": "Main entfernen",
+    "removeTheirs": "Incoming entfernen",
     "continue": "Lösen & fortfahren",
     "abort": "Merge abbrechen"
   },

src/ClaudeDo.Localization/locales/en.json

@@ -400,15 +400,16 @@
     "windowTitle": "Resolve merge conflicts",
     "modalTitle": "RESOLVE CONFLICTS",
     "loading": "Loading conflicts…",
-    "ours": "OURS · current (merge target)",
+    "ours": "MAIN · merge target",
     "result": "RESULT",
-    "theirs": "THEIRS · incoming (task)",
+    "theirs": "INCOMING · task branch",
     "binaryHint": "Binary files can't be merged here — abort and resolve them in your editor:",
     "prevConflict": "Previous conflict (Shift+F8)",
     "nextConflict": "Next conflict (F8)",
-    "acceptOurs": "Add ours (stacks in click order)",
-    "acceptTheirs": "Add theirs (stacks in click order)",
-    "clearConflict": "Clear this conflict (start over)",
+    "acceptOurs": "Add main",
+    "acceptTheirs": "Add incoming",
+    "removeOurs": "Remove main",
+    "removeTheirs": "Remove incoming",
     "continue": "Resolve & continue",
     "abort": "Abort merge"
   },