the store keeps a routing trace for fourteen days (V-629)

Migration #23 adds routing_traces, and internal/store/routingtraces.go writes,
lists and prunes it. Nothing calls it yet; the daemon side is the next commit.

The utterance is stored in clear. A 384-dimension vector of a short sentence is
substantially recoverable, so storing vectors instead would be a privacy claim
we cannot support. Retention is 14 days, enforced on write, and an age rather
than a row count so a busy Tuesday cannot push last Friday out. Store.Wipe
already deletes it with everything else, so explicit deletion needs no new
surface.

A correction is not covered by that bound. When the owner corrects a turn the
pair is promoted out into a seed-shaped row and kept, because a label is not a
transcript. What stays here is the transcript, and the transcript expires.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0117tgnmbgZpHVV3XSNw8Qua

internal/store/migrations.go

@@ -300,6 +300,36 @@ ALTER TABLE reminders ADD COLUMN next_fire_ts INTEGER;`, // #2
 	// here and no caller has to tell them apart.
 	`ALTER TABLE tasks ADD COLUMN done_when TEXT NOT NULL DEFAULT '';
 	 ALTER TABLE tasks ADD COLUMN blocked_on TEXT NOT NULL DEFAULT '';`,
+	// #23 — the routing trace (V-629). internal/decision kept a 25-turn ring and
+	// persisted nothing, on the argument that a turn record is read minutes later
+	// or never. The owner reversed that on 06-08-2026: mode discovery and distance
+	// calibration need real utterances, and there is no other source of them.
+	// docs/plans/21-persisting-the-routing-trace.md carries the
+	// reversal.
+	//
+	// utterance holds his words in clear. A 384-dimension vector of a short
+	// sentence is substantially recoverable, so storing vectors instead would be a
+	// privacy claim we cannot support. What makes it safe is the same thing that
+	// makes the fact store safe: it never leaves the box, retention is bounded at
+	// routingTraceRetention, and Wipe drops it with everything else.
+	//
+	// correction is empty until the owner corrects a turn on /chat (V-630). A
+	// corrected pair is promoted out of here into a seed-shaped row and kept, so
+	// this column is a queue, not the durable label.
+	`CREATE TABLE IF NOT EXISTS routing_traces (
+		id                  INTEGER PRIMARY KEY AUTOINCREMENT,
+		ts                  INTEGER NOT NULL,
+		utterance           TEXT    NOT NULL,
+		source              TEXT    NOT NULL DEFAULT '',
+		winner              TEXT    NOT NULL DEFAULT '',
+		intent              TEXT    NOT NULL DEFAULT '',
+		claimed_before_head INTEGER NOT NULL DEFAULT 0,
+		encoder_id          TEXT    NOT NULL DEFAULT '',
+		outcome             TEXT    NOT NULL DEFAULT '',
+		correction          TEXT    NOT NULL DEFAULT '',
+		claims              TEXT    NOT NULL DEFAULT '[]'
+	);
+	CREATE INDEX IF NOT EXISTS idx_routing_traces_ts ON routing_traces (ts DESC);`,
 }
 
 // migrate applies every migration with a number greater than the DB's current