fix(store): expand a leading ~ in EMCLI_DB

A literal "~/..." in EMCLI_DB has no shell to expand it, so SQLite opened
it relative to the cwd and silently created a stray "~" directory tree.
Expand a leading "~" or "~/" to the user's home dir; "~user", mid-path
tildes, and absolute/relative paths are left untouched.

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

internal/store/store_test.go

@@ -2,10 +2,53 @@ package store
 
 import (
 	"database/sql"
+	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
+// A leading "~" in EMCLI_DB must be expanded to the home dir, so a literal
+// tilde (no shell to expand it) can't be opened relative to the cwd and
+// silently create a stray "~" directory.
+func TestDefaultDBPathExpandsLeadingTilde(t *testing.T) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Skipf("no home dir: %v", err)
+	}
+	cases := map[string]string{
+		"~/.config/emcli/emcli.db": filepath.Join(home, ".config", "emcli", "emcli.db"),
+		"~":                        home,
+	}
+	for in, want := range cases {
+		t.Setenv("EMCLI_DB", in)
+		got, err := DefaultDBPath()
+		if err != nil {
+			t.Fatalf("DefaultDBPath(%q): %v", in, err)
+		}
+		if got != want {
+			t.Fatalf("EMCLI_DB=%q -> %q, want %q", in, got, want)
+		}
+		if strings.Contains(got, "~") {
+			t.Fatalf("EMCLI_DB=%q left a literal tilde: %q", in, got)
+		}
+	}
+}
+
+// A non-leading tilde or "~user" is NOT a path we should rewrite — leave it be.
+func TestDefaultDBPathLeavesOtherPathsUntouched(t *testing.T) {
+	for _, p := range []string{"/var/lib/emcli.db", "./rel/emcli.db", "~user/db"} {
+		t.Setenv("EMCLI_DB", p)
+		got, err := DefaultDBPath()
+		if err != nil {
+			t.Fatalf("DefaultDBPath(%q): %v", p, err)
+		}
+		if got != p {
+			t.Fatalf("EMCLI_DB=%q was rewritten to %q", p, got)
+		}
+	}
+}
+
 // openTemp opens a fresh store in a temp dir and initialises keys so that
 // account tests (which do crypto) work without needing their own setup.
 func openTemp(t *testing.T) *Store {