replace Redis with an embedded SQLite string->string KV store (group commit, in-tx events, SQL search)

internal/api/stats.go

@@ -27,8 +27,10 @@ type fileStatsJSON struct {
 // dashboard shows, in one request.
 //
 // Deliberately split by cost. Records/RedisKeys/RedisMemory/Identities are
-// O(1) commands (SCARD, DBSIZE, INFO) plus a directory listing, recomputed on
-// every call. Files and UDLUsers need a keyspace walk — ~0.5s for the file
+// cheap (an index range count, a cached row count, a file stat) plus a
+// directory listing, recomputed on every call. The `redis*` JSON names
+// predate the move to SQLite and are kept for dashboard compatibility:
+// redisKeys is the store's row count, redisMemory its on-disk size. Files and UDLUsers need a keyspace walk — ~0.5s for the file
 // tuples and ~3s for the UDL SCAN on an 88k-record box — so they are served
 // from a background-refreshed cache and are null until the first sweep lands.
 type StatsResponse struct {
@@ -47,7 +49,7 @@ type StatsResponse struct {
 
 // statsCache holds the expensive half of /api/stats.
 //
-// Why a cache and not just "compute it": the dashboard polls. A 3s Redis walk
+// Why a cache and not just "compute it": the dashboard polls. A multi-second store walk
 // per tick, per open tab, is a self-inflicted outage on a box that is also
 // serving playback — the same shape as meta-sort's /api/stats full sweep. So
 // the handler NEVER waits on a walk: it returns whatever the last sweep
@@ -86,7 +88,7 @@ func (c *statsCache) refreshIfStale(sweep func() (*fileStatsJSON, *int)) bool {
 		c.running = false
 		// A failed sweep leaves the previous numbers in place rather than
 		// blanking the tiles; sweptAt still advances so a hard-failing walk
-		// (Redis down) does not spin once per poll.
+		// (store down) does not spin once per poll.
 		c.sweptAt = time.Now()
 		if files != nil {
 			c.files = files