refactor(console): phase 0 — remove dead code + fix channel/arg bugs

Zero-behavior-change cleanup ahead of the console refactor:
- Delete dead API/members: addCommandResult (unused), handleSelection (declared, no
  def), isAutoScrollEnabled (no callers), and scroll_to_bottom_ (written 8× but never
  read) with all its writes.
- Drop the unused screenToTextPos `line_height` parameter (+ 4 call sites) and the unused
  `segEnd` local — clears the two -Wunused warnings.
- Remove the toolbar filter checkboxes' dead `static bool s_prev_*` change-detectors,
  whose only effect was setting the dead scroll_to_bottom_.
- Fix the console_new_lines format/arg mismatch (format takes one %d; the call passed a
  spurious plural-suffix arg).
- Fix the channel/color incoherence: a "[daemon] error:" line kept red text but got a
  blue daemon bar — the prefix no longer downgrades an error channel.
- Delete 11 orphaned lite_console_* i18n keys left over from the console merge (keep
  lite_console_help_passthrough).

Full-node + lite build clean, ctest green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/util/i18n.cpp

@@ -1223,17 +1223,6 @@ void I18n::loadBuiltinEnglish()
         strings_["daemon_update_downgrade_note"]   = "Older versions may be incompatible with your current chain data. Installing a different version takes effect after a daemon restart.";
 
         // --- Lite Network tab (server browser) ---
-        strings_["lite_console_title"]      = "Console";
-        strings_["lite_console_intro"]      = "Diagnostic log + interactive console. Type a command (e.g. info, balance, list) and press Enter; type help for the full list.";
-        strings_["lite_console_status"]     = "Status:";
-        strings_["lite_console_clear"]      = "Clear";
-        strings_["lite_console_copy"]       = "Copy";
-        strings_["lite_console_autoscroll"] = "Auto-scroll";
-        strings_["lite_console_empty"]      = "No output yet. Type a command (try 'help') and press Enter.";
-        strings_["lite_console_input_hint"] = "Type a command (help, info, balance, list, sync, new zs)…";
-        strings_["lite_console_running"]    = "running…";
-        strings_["lite_console_busy"]       = "A command is already running — wait for it to finish.";
-        strings_["lite_console_quit_note"]  = "'quit'/'exit' don't apply here — the embedded backend stays running with the app.";
         strings_["lite_net_title"]        = "Lite Servers";
         strings_["lite_net_intro"]        = "Pick a server to use, or let the wallet choose one at random. Changes apply immediately.";
         strings_["lite_net_use_random"]   = "Use a random server each time";