Split evidence-stats accounting into stats.go

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/session/session.go

@@ -96,21 +96,6 @@ var ErrNotPlanning = errors.New("session: coaching is only available while plann
 
 var ErrNotActive = errors.New("session: only available while a commitment is active")
 
-// bucketKey identifies a time bucket; Title is the scrubbed title.
-type bucketKey struct{ Class, Title string }
-
-// EvidenceStats is the in-memory accounting for the current session only.
-type EvidenceStats struct {
-	SessionID   string
-	StartedUnix int64
-	Buckets     map[bucketKey]time.Duration
-	SwitchCount int
-	Current     evidence.WindowSnapshot
-	lastFocusAt time.Time
-	lastKey     bucketKey
-	hasLast     bool
-}
-
 // Controller holds runtime state and the active commitment behind a mutex.
 type Controller struct {
 	mu             sync.Mutex
@@ -1031,66 +1016,3 @@ func (c *Controller) applyVerdictLocked(v ai.Verdict) {
 	c.driftStatus = driftDrifting
 	c.driftReason = v.Reason
 }
-
-// applyEvent advances stats by one observation: it credits the prior segment to
-// the prior bucket, counts a context switch on key change, and records the new
-// current window. Used by both live tracking and crash replay. Caller holds mu.
-func (c *Controller) applyEvent(now time.Time, snap evidence.WindowSnapshot) {
-	if c.stats.hasLast {
-		c.stats.Buckets[c.stats.lastKey] += now.Sub(c.stats.lastFocusAt)
-	}
-	newKey := keyFor(snap)
-	if c.stats.hasLast && newKey != c.stats.lastKey {
-		c.stats.SwitchCount++
-	}
-	c.stats.lastKey = newKey
-	c.stats.lastFocusAt = now
-	c.stats.hasLast = true
-	c.stats.Current = snap
-}
-
-// replayStats rebuilds in-memory stats from the raw session log after a crash.
-func (c *Controller) replayStats(sessionID string) {
-	events, err := store.ReplaySession(c.sessionsDir, sessionID)
-	if err != nil || len(events) == 0 {
-		c.stats = &EvidenceStats{
-			SessionID:   sessionID,
-			StartedUnix: c.clock().Unix(),
-			Buckets:     map[bucketKey]time.Duration{},
-		}
-		return
-	}
-	c.stats = &EvidenceStats{
-		SessionID:   sessionID,
-		StartedUnix: events[0].AtUnixMillis / 1000,
-		Buckets:     map[bucketKey]time.Duration{},
-	}
-	for _, e := range events {
-		c.applyEvent(time.UnixMilli(e.AtUnixMillis), snapFromEvent(e))
-	}
-}
-
-func keyFor(snap evidence.WindowSnapshot) bucketKey {
-	if !snap.Health.Available {
-		return bucketKey{Class: "", Title: unavailableTitle}
-	}
-	return bucketKey{Class: snap.Class, Title: evidence.ScrubTitle(snap.Title)}
-}
-
-func focusEvent(now time.Time, snap evidence.WindowSnapshot) store.FocusEvent {
-	return store.FocusEvent{
-		AtUnixMillis: now.UnixMilli(),
-		Class:        snap.Class,
-		Title:        snap.Title,
-		Available:    snap.Health.Available,
-		Reason:       snap.Health.Reason,
-	}
-}
-
-func snapFromEvent(e store.FocusEvent) evidence.WindowSnapshot {
-	return evidence.WindowSnapshot{
-		Title:  e.Title,
-		Class:  e.Class,
-		Health: evidence.EvidenceHealth{Available: e.Available, Reason: e.Reason},
-	}
-}