feat: e opens a repo's SOPS or .env file, in nvim, sops edit or your editor (#1)

`e` on a file in a repo opens it; on a secret, it opens the file at that key's line.

- **SOPS files**: `sops edit` in the terminal, then back to lazysecrets with the keys reloaded. Exit 200 (nothing changed) shows "unchanged".
- **Other files inside nvim** (`$NVIM` set): lazysecrets asks that nvim, over `--remote-expr`, to open the file once lazysecrets' terminal closes, then quits. The file lands in the window you came from, not the closing float. Started from a shell in a terminal, it opens in the previous window straight away. No change to the nvim plugin is needed.
- **Otherwise**: `$VISUAL`/`$EDITOR` in the terminal (with `+N`, `file:N` or `-g file:N` for editors that take a line), else the system default app.

The repo provider now records each key's line (YAML node lines, env/ini line numbers) behind a new optional `provider.Files` interface. Other providers show "only SOPS and .env files in repos can be opened".

The nvim handoff was tested against a headless nvim 0.12: a floating terminal closed on exit the way snacks does, and a shell in a split. A file name with a space and a quote opened at the right line in both. Unit tests cover lines per format, the nvim, sops and default-app paths, and the editor line arguments.

Note: `e` is a new default key, so a config that already binds `e` to something else now gets the "bound to both" error, until one of them is rebound.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>
Reviewed-on: #1

internal/ui/app/app.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"image/color"
 	"math"
+	"os"
 	"os/exec"
 	"strings"
 	"time"
@@ -156,6 +157,8 @@ type Model struct {
 	clip      Clipboard
 	clipClear time.Duration
 	openURL   func(string) error
+	getenv    func(string) string
+	nvimOpen  func(server, path string, line int) error // edit.go
 	now       func() time.Time
 
 	// A pending clear of a copied value, counted down in the footer.
@@ -337,6 +340,8 @@ func New(providers []provider.Provider, opts Options) Model {
 		clip:          opts.Clipboard,
 		clipClear:     opts.ClipboardClear,
 		now:           time.Now,
+		getenv:        os.Getenv,
+		nvimOpen:      nvimOpen,
 		cache:         newCache(),
 	}
 	if m.clip == nil {
@@ -522,6 +527,9 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	case commandDoneMsg:
 		m.handleCommandDone(msg)
 
+	case editDoneMsg:
+		cmds = append(cmds, m.handleEditDone(msg))
+
 	case crawlMsg:
 		cmds = append(cmds, m.handleCrawl(msg))
 
@@ -833,6 +841,8 @@ func (m *Model) handleKey(msg tea.KeyPressMsg) (cmd tea.Cmd, quit bool) {
 		}
 	case key.Matches(msg, k.Open):
 		return m.openSelected(), false
+	case key.Matches(msg, k.Edit):
+		return m.edit(), false
 	case key.Matches(msg, k.Login):
 		if m.auth != nil && len(m.auth.Login) > 0 {
 			c := exec.Command(m.auth.Login[0], m.auth.Login[1:]...)