feat(cli): tapir report — Stage-0 usage gate query

ActiveWeeks computes per-user distinct active weeks (reads login_events UNION
acts summary_actions) for the gate (VISION/ADR-016: usage in >=2 distinct
weeks). Because the user-owned tables are FORCE RLS under a non-superuser owner,
a single cross-user query is deny-all; instead it enumerates users from the
un-RLS'd identity map and counts each inside withUser — no privilege escalation,
no policy change.

`tapir report` prints the per-user table and the pass/fail verdict (needs only
TAPIR_DB_DSN). Pure formatter + store query are unit-tested, including the
cross-table shared-week dedup.

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

cmd/tapir/report.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"text/tabwriter"
+
+	"gitea.d-ma.be/mathias/tapir/internal/adapters/store"
+)
+
+// gateThreshold is the Stage-0 gate (VISION/ADR-016): usage in >= 2 distinct
+// weeks. The gate passes when any user reaches it.
+const gateThreshold = 2
+
+// runReport prints the Stage-0 usage gate: per-user distinct active weeks (reads
+// UNION acts) and the pass/fail verdict. Read-only, cross-user — needs only
+// TAPIR_DB_DSN (not TAPIR_USER_ID; the report enumerates all users itself).
+func runReport(ctx context.Context, _ []string) error {
+	dsn := os.Getenv(envDSN)
+	if dsn == "" {
+		return fmt.Errorf("%s is required", envDSN)
+	}
+	s, err := store.New(ctx, dsn)
+	if err != nil {
+		return err
+	}
+	defer s.Close()
+
+	rows, err := s.ActiveWeeks(ctx)
+	if err != nil {
+		return err
+	}
+	return formatReport(os.Stdout, rows)
+}
+
+// formatReport renders the per-user week counts and the gate verdict. Pure: no DB,
+// no env — so the layout and verdict logic are unit-testable without Postgres.
+func formatReport(w io.Writer, rows []store.UserActiveWeeks) error {
+	if len(rows) == 0 {
+		_, err := fmt.Fprintln(w, "no users yet")
+		return err
+	}
+
+	tw := tabwriter.NewWriter(w, 0, 4, 2, ' ', 0)
+	_, _ = fmt.Fprintln(tw, "USER\tNAME\tACTIVE_WEEKS\tGATE")
+	passed := false
+	for _, r := range rows {
+		gate := "-"
+		if r.ActiveWeeks >= gateThreshold {
+			gate = "PASS"
+			passed = true
+		}
+		_, _ = fmt.Fprintf(tw, "%s\t%s\t%d\t%s\n", r.UserID, orDash(r.DisplayName), r.ActiveWeeks, gate)
+	}
+	if err := tw.Flush(); err != nil {
+		return err
+	}
+
+	verdict := fmt.Sprintf("\nGate (usage in >= %d distinct weeks): NOT YET MET\n", gateThreshold)
+	if passed {
+		verdict = fmt.Sprintf("\nGate (usage in >= %d distinct weeks): PASSED\n", gateThreshold)
+	}
+	_, err := fmt.Fprint(w, verdict)
+	return err
+}