feat(observabilidade): tabela patterns + 6 detectores SQL

Adiciona tabela 'patterns' à BD sessions (UNIQUE por week_iso+pattern_key)
e helpers upsertPattern/getPatternsByWeek/getConsecutiveWeeks no SessionsDb.

Módulo patterns.ts implementa 6 detectores heurísticos para deteccão semanal:
  1. skills_with_high_error_rate (ratio > 0.2, severity warning|action)
  2. tools_low_efficiency (tool_calls/event_count médio > 0.5)
  3. skill_tool_pairs (top 5 co-ocorrências)
  4. duration_outliers (sessões > p95 com outcome != completed)
  5. abandoned_sessions (event_count<3 AND outcome=unknown, >=5)
  6. growing_complexity (avg tool_calls actual > anterior*1.3)

5 testes cobrem detector de erro, abandonadas, consecutive_weeks,
idempotência do upsert e toPatternRecord.

Refs Fase 6A · Desk #2059 · Project #65

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/services/sessions/db.ts

@@ -13,6 +13,20 @@ export interface ListFilters {
   offset?: number
 }
 
+export interface PatternRecord {
+  id?: number
+  detected_at: string
+  week_iso: string
+  pattern_key: string
+  title: string
+  description: string
+  severity: 'info' | 'warning' | 'action'
+  metric_value: number | null
+  sample_session_ids: string[]
+  affected_count: number
+  consecutive_weeks: number
+}
+
 export interface SessionsDb {
   upsertSession(meta: SessionMeta): void
   upsertMany(metas: SessionMeta[]): void
@@ -20,6 +34,10 @@ export interface SessionsDb {
   countSessions(filters: ListFilters): number
   getSession(id: string): SessionMeta | null
   deleteByJsonlPath(path: string): void
+  upsertPattern(p: PatternRecord): void
+  getPatternsByWeek(week: string): PatternRecord[]
+  getConsecutiveWeeks(pattern_key: string, uptoWeek: string): number
+  rawDb(): Database.Database
   close(): void
 }
 
@@ -46,6 +64,23 @@ CREATE TABLE IF NOT EXISTS sessions (
 );
 CREATE INDEX IF NOT EXISTS idx_started ON sessions(started_at DESC);
 CREATE INDEX IF NOT EXISTS idx_project ON sessions(project_slug, started_at DESC);
+
+CREATE TABLE IF NOT EXISTS patterns (
+  id              INTEGER PRIMARY KEY AUTOINCREMENT,
+  detected_at     TEXT NOT NULL,
+  week_iso        TEXT NOT NULL,
+  pattern_key     TEXT NOT NULL,
+  title           TEXT NOT NULL,
+  description     TEXT NOT NULL,
+  severity        TEXT NOT NULL,
+  metric_value    REAL,
+  sample_session_ids TEXT NOT NULL,
+  affected_count  INTEGER NOT NULL,
+  consecutive_weeks INTEGER NOT NULL DEFAULT 1,
+  UNIQUE(week_iso, pattern_key)
+);
+CREATE INDEX IF NOT EXISTS idx_patterns_week ON patterns(week_iso);
+CREATE INDEX IF NOT EXISTS idx_patterns_key ON patterns(pattern_key);
 `
 
 function rowToMeta(row: Record<string, unknown>): SessionMeta {
@@ -177,8 +212,92 @@ export function openSessionsDb(dbPath: string): SessionsDb {
     deleteByJsonlPath(path) {
       db.prepare('DELETE FROM sessions WHERE jsonl_path = ?').run(path)
     },
+    upsertPattern(p: PatternRecord) {
+      db.prepare(`
+        INSERT INTO patterns (detected_at, week_iso, pattern_key, title, description,
+          severity, metric_value, sample_session_ids, affected_count, consecutive_weeks)
+        VALUES (@detected_at, @week_iso, @pattern_key, @title, @description,
+          @severity, @metric_value, @sample_session_ids, @affected_count, @consecutive_weeks)
+        ON CONFLICT(week_iso, pattern_key) DO UPDATE SET
+          detected_at = excluded.detected_at,
+          title = excluded.title,
+          description = excluded.description,
+          severity = excluded.severity,
+          metric_value = excluded.metric_value,
+          sample_session_ids = excluded.sample_session_ids,
+          affected_count = excluded.affected_count,
+          consecutive_weeks = excluded.consecutive_weeks
+      `).run({
+        detected_at: p.detected_at,
+        week_iso: p.week_iso,
+        pattern_key: p.pattern_key,
+        title: p.title,
+        description: p.description,
+        severity: p.severity,
+        metric_value: p.metric_value,
+        sample_session_ids: JSON.stringify(p.sample_session_ids),
+        affected_count: p.affected_count,
+        consecutive_weeks: p.consecutive_weeks,
+      })
+    },
+    getPatternsByWeek(week: string): PatternRecord[] {
+      const rows = db.prepare('SELECT * FROM patterns WHERE week_iso = ? ORDER BY severity DESC, affected_count DESC').all(week) as Record<string, unknown>[]
+      return rows.map((r) => ({
+        id: r.id as number,
+        detected_at: r.detected_at as string,
+        week_iso: r.week_iso as string,
+        pattern_key: r.pattern_key as string,
+        title: r.title as string,
+        description: r.description as string,
+        severity: r.severity as PatternRecord['severity'],
+        metric_value: (r.metric_value as number | null) ?? null,
+        sample_session_ids: JSON.parse(r.sample_session_ids as string),
+        affected_count: r.affected_count as number,
+        consecutive_weeks: r.consecutive_weeks as number,
+      }))
+    },
+    getConsecutiveWeeks(pattern_key: string, uptoWeek: string): number {
+      // Conta semanas consecutivas até uptoWeek (inclusive) em que pattern_key apareceu
+      const rows = db.prepare('SELECT DISTINCT week_iso FROM patterns WHERE pattern_key = ? AND week_iso <= ? ORDER BY week_iso DESC').all(pattern_key, uptoWeek) as { week_iso: string }[]
+      if (rows.length === 0) return 0
+      let count = 0
+      let cursor = uptoWeek
+      for (const row of rows) {
+        if (row.week_iso === cursor) {
+          count++
+          cursor = prevWeekIso(cursor)
+        } else {
+          break
+        }
+      }
+      return count
+    },
+    rawDb(): Database.Database {
+      return db
+    },
     close() {
       db.close()
     },
   }
 }
+
+/** Calcula semana ISO anterior (YYYY-Www). */
+export function prevWeekIso(week: string): string {
+  const m = week.match(/^(\d{4})-W(\d{2})$/)
+  if (!m) return week
+  const year = parseInt(m[1], 10)
+  const w = parseInt(m[2], 10)
+  if (w > 1) return `${year}-W${String(w - 1).padStart(2, '0')}`
+  // Semana 1 → última semana do ano anterior (52 ou 53)
+  const prevYear = year - 1
+  const last = weeksInYear(prevYear)
+  return `${prevYear}-W${String(last).padStart(2, '0')}`
+}
+
+function weeksInYear(year: number): number {
+  // ISO: ano tem 53 semanas se 1 Jan é quinta ou (ano bissexto e 1 Jan é quarta)
+  const jan1 = new Date(Date.UTC(year, 0, 1)).getUTCDay()
+  const isLeap = (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0
+  if (jan1 === 4 || (isLeap && jan1 === 3)) return 53
+  return 52
+}