fix: unambiguous repo key names, clearer config and key names, and a newer lazysecrets's files no longer stop an older one (#66)

Changes that would break configs or links once people use lazysecrets, made while nobody does yet.

- **Repo key names**: a dot or bracket inside a key is escaped (`app\.name`), so links to it resolve to that key and not to `app` → `name`. Dotenv files are flat, so their names stay as they are.
- **Config**: `updates.updateSources` is now `updates.sources`. A negative provider timeout, or `--timeout` of 0 or less, is an error instead of making every request fail.
- **Keybindings**: `lists.share` is now `lists.copyLink`, `lists.search` is `lists.goTo` and `lists.enter` is `lists.open`, matching what they do.
- **Version skew**, e.g. a lazysecrets.nvim theme file made for a newer lazysecrets:
  - an unknown theme role is skipped with a warning instead of stopping startup;
  - a state file from a newer version is read but not saved to, with a warning;
  - a link with an unknown provider suggests `lazysecrets update`.

Reviewed-on: #66
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>

internal/store/store_test.go

@@ -1,6 +1,7 @@
 package store
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -65,11 +66,17 @@ func TestTwoWindowsDontLoseEachOthersChanges(t *testing.T) {
 	}
 }
 
-func TestNewerVersionRefused(t *testing.T) {
+func TestNewerVersionReadOnly(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "state.json")
-	_ = os.WriteFile(path, []byte(`{"version": 99, "nodes": {}}`), 0o600)
-	if _, err := Load(path); err == nil {
-		t.Error("a newer file was accepted")
+	newer := `{"version": 99, "nodes": {"one": {"note": "hi"}}}`
+	_ = os.WriteFile(path, []byte(newer), 0o600)
+	s, err := Load(path)
+	if !errors.Is(err, ErrNewer) || s == nil || s.Node("one").Note != "hi" {
+		t.Fatalf("Load = %v, %v", s, err)
+	}
+	_ = s.SetFlag("x", true)
+	if b, _ := os.ReadFile(path); string(b) != newer {
+		t.Errorf("the newer file was overwritten: %s", b)
 	}
 }