Split session time into on/off/unclassified buckets

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

internal/session/session.go

@@ -249,6 +249,8 @@ func (c *Controller) StartManualCommitment(nextAction, successCondition string,
 		SessionID:   sessionID,
 		StartedUnix: now.Unix(),
 		Buckets:     map[bucketKey]time.Duration{},
+		OnTask:      map[bucketKey]time.Duration{},
+		OffTask:     map[bucketKey]time.Duration{},
 	}
 	seed := c.latestWindow
 	_ = store.AppendFocus(c.sessionsDir, sessionID, focusEvent(now, seed))
@@ -278,7 +280,7 @@ func (c *Controller) enterReview(outcome string) error {
 	}
 	// Flush the final open segment, then freeze accounting.
 	if c.stats != nil && c.stats.hasLast {
-		c.stats.Buckets[c.stats.lastKey] += c.clock().Sub(c.stats.lastFocusAt)
+		c.creditLocked(c.stats.lastKey, c.clock().Sub(c.stats.lastFocusAt))
 		c.stats.hasLast = false
 	}
 	c.runtimeState = next