fix(ui): report failed paste/drop in the interactive terminal

PasteAsync silently swallowed every exception and returned void, so a
package update renaming Iciclecreek's private write seam would break
Ctrl+V/drop with zero user-visible signal. PasteAsync/SendTextAsync now
return bool (mirroring SendLineAsync), and the view checks the result,
routing a failure through InteractiveTerminalViewModel.ErrorReported ->
ConPtyPaneViewModel.ErrorReported -> the existing footer error strip.

src/ClaudeDo.Localization/locales/en.json

@@ -384,6 +384,7 @@
     "conptyStarting": "Starting session…",
     "conptyExited": "Session ended (code {0}).",
     "usageWarningNotDelivered": "Couldn't warn the list-handler session about the usage limit.",
+    "terminalSendFailed": "Couldn't send that to the terminal session.",
     "mergeHelperTitle": "Merge Helper",
     "mergeHelperHandoffTitleSuffix": " (Handoff)",
     "mergeHelperTaskTitle": "List handler: {0}",