v2 Phase 4: add "generated" (output) tokens under the total on Session

The total is ~97% cache reads, which reads as implausibly large on its own.
Show the cache-inclusive total as the headline token number and the output
tokens ("what Claude actually generated", ~1.1M) as a small line beneath it —
impressive total, believable sub-number. Daemon sends a new `to` field; firmware
parses output_today and renders it. Re-spaced the Session layout for the 5th row.

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

firmware/src/main.cpp

@@ -113,6 +113,7 @@ static bool parse_json(const char* json, UsageData* out) {
     strlcpy(out->status, doc["st"] | "unknown", sizeof(out->status));
     out->ok = doc["ok"] | false;
     out->tokens_today = doc["tk"] | (long long)0;
+    out->output_today = doc["to"] | (long long)0;
     out->cost_cents_today = doc["tc"] | 0;
     out->messages_today = doc["tn"] | 0;
     out->valid = true;