fix(lite): always-populated Console (live status) + single-instance log

The Console could look empty if the wallet produced few events. Make it useful
in every state and remove a cross-platform footgun:

- Add a live status header read straight from the controller (connected /
  connecting / disconnected, sync %, and the last open error) — independent of the
  diagnostics event log, so the Console always shows the current connection +
  wallet-open state even when the log is sparse.
- Move LiteDiagnostics::instance() into a single .cpp so there is exactly one
  instance across the binary, rather than relying on the linker folding an
  inline-function static across translation units (a known fragility, especially
  on mingw/Windows — the most likely cause of a stuck-empty event log there).

Verified the writer and reader share one instance on Linux; builds clean for
full-node, lite, and Windows cross-compile; tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CMakeLists.txt

@@ -409,6 +409,7 @@ set(APP_SOURCES
     src/wallet/lite_rollout_policy.cpp
     src/wallet/lite_client_bridge.cpp
     src/wallet/lite_connection_service.cpp
+    src/wallet/lite_diagnostics.cpp
     src/wallet/lite_wallet_controller.cpp
     src/wallet/lite_result_parsers.cpp
     src/wallet/lite_sync_service.cpp
@@ -962,6 +963,7 @@ if(BUILD_TESTING)
         src/wallet/lite_rollout_policy.cpp
         src/wallet/lite_client_bridge.cpp
         src/wallet/lite_connection_service.cpp
+        src/wallet/lite_diagnostics.cpp
         src/wallet/lite_wallet_controller.cpp
         src/wallet/lite_result_parsers.cpp
         src/wallet/lite_sync_service.cpp