fix: store per-turn token sums so searched turns price every round

A searched turn makes one API call per search round and all of them are
billed, but prompt_tokens/completion_tokens held only the last round's
counts, so a searched turn under-reported its cost. The columns now hold
the sum across rounds; usage_json keeps each round's raw usage block as
a JSON array for external consumers to verify against. A single-round
turn stores the same numbers as before.

1 files changed, 6 insertions, 5 deletions

diff --git a/README.md b/README.md
index 416a84c..f53d167 100644
--- a/README.md
+++ b/README.md
@@ -312,11 +312,12 @@ web pages would compete with messages the user actually wrote.
 `provider` records which provider served the reply (`local` or a configured
 provider name), written when the reply finishes so history stays
 self-describing even if `config.toml` later renames or drops the provider.
-`usage_json` keeps every round's raw usage block from the stream as a JSON
-array — a searched turn makes one API call per search round, and each round
-is billed separately, so all of them are kept verbatim and token details
-beyond the two counts (e.g. cached or reasoning tokens on a cloud endpoint)
-are recoverable later without re-guessing a field mapping.
+`prompt_tokens` and `completion_tokens` hold the turn's totals summed across
+every round — a searched turn makes one API call per search round and all of
+them are billed, so the last round's counts alone would under-report it.
+`usage_json` keeps each round's raw usage block as a JSON array, verbatim, so
+token details beyond the two counts (e.g. cached or reasoning tokens on a
+cloud endpoint) are recoverable later without re-guessing a field mapping.
 `reported_cost_usd` is the GUI's hand-entered-price estimate for that one
 reply (summed across rounds), stored as a sanity check for external
 consumers — it is approximate and never a source of truth; it stays NULL for