feat: keep what was loaded between runs, and start where you left off (#2)

Starting lazysecrets again now shows what you had loaded at once, and puts you back where you were.

- **Cache file** `~/.cache/lazysecrets/cache.json` (0600, written atomically): the Sources lists, vaults/scopes, secrets' metadata, Describe results and each list's cursor. **Never values**, and never repos (they're on disk anyway). Loaded on start; lists older than 2 minutes reload in the background as before. Saved every 30s when changed, and on quit.
- **Housekeeping:** entries not loaded for 30 days are dropped, as is everything from accounts no longer signed in (every cache key starts with the account ID). The file has a format version; another version is ignored and replaced. `cache: false` turns it off; `--demo` never uses it.
- **Sources are cached too:** Azure lists subscriptions over the network, so without this the Sources pane would still wait.
- **Go to** searches everything cached straight away, and its background loading now also refreshes lists from an earlier run instead of skipping them.
- **Where you left off:** the state file remembers the selected source, vault or secret per folder (the `--dir` or working directory, 100 most recent folders), and the next start in that folder goes back there quietly (no error if it's gone). Starting on a link skips it.

Docs: `cache:` in config.md, a Cache section, the place in State, and the README Privacy section now mentions the cache file.

Tests: cache round trip with a backend too slow to answer (lists and cursor come from the file), no value in the file, file mode 0600, old and signed-out entries dropped, back where it was left, not for another folder or a link.

This touches `app.go` near PR #1's changes (Model fields, the Update switch), so whichever merges second needs a small conflict fix.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>
Reviewed-on: #2

internal/ui/app/app.go

@@ -69,6 +69,12 @@ type Options struct {
 	ClipboardClear time.Duration
 	// OpenURL opens a web page; defaults to the system browser.
 	OpenURL func(url string) error
+	// CacheFile keeps what was loaded between runs; "" keeps it for this
+	// run only.
+	CacheFile string
+	// Dir is the folder lazysecrets runs in: it goes back to where it was
+	// left there, unless it was started on a link. "" doesn't.
+	Dir string
 	// FlatSources lists sources without provider groups.
 	FlatSources bool
 	// CollapseGroups starts with the Sources pane's groups folded, when
@@ -160,6 +166,13 @@ type Model struct {
 	getenv    func(string) string
 	nvimOpen  func(server, path string, line int) error // edit.go
 	now       func() time.Time
+	// The cache file, whether the cache changed since it was saved, and
+	// when each provider's Sources list was loaded (persist.go).
+	cachePath  string
+	cacheDirty bool
+	sourcesAt  map[string]time.Time
+	placeDir   string
+	savedPlace string // the link last saved as the place
 
 	// A pending clear of a copied value, counted down in the footer.
 	// clipToken identifies the latest copy so older ticks are ignored.
@@ -415,6 +428,17 @@ func New(providers []provider.Provider, opts Options) Model {
 	m.sourcesGen = 1
 	m.sourcesPending = len(providers)
 	m.spinning = true
+
+	m.cachePath, m.placeDir, m.sourcesAt = opts.CacheFile, opts.Dir, map[string]time.Time{}
+	if m.cachePath != "" {
+		m.loadCacheFile()
+		if len(m.sourceResults) > 0 {
+			m.rebuildSources()
+		}
+	}
+	if m.placeDir != "" && opts.Open == nil {
+		m.restorePlace()
+	}
 	return m
 }
 
@@ -438,6 +462,9 @@ func (m *Model) setVersions(items []provider.Object) {
 
 func (m Model) Init() tea.Cmd {
 	cmds := []tea.Cmd{m.sourcesCmd(), m.spin.Tick, m.checkClipboard()}
+	if m.cachePath != "" || m.placeDir != "" {
+		cmds = append(cmds, tea.Tick(persistEvery, func(time.Time) tea.Msg { return persistTickMsg{} }))
+	}
 	if m.fetchOnStart {
 		cmds = append(cmds, m.fetchLatest(false))
 	}
@@ -530,6 +557,12 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	case editDoneMsg:
 		cmds = append(cmds, m.handleEditDone(msg))
 
+	case persistTickMsg:
+		cmds = append(cmds, m.persistTick())
+
+	case persistedMsg:
+		m.handlePersisted(msg)
+
 	case crawlMsg:
 		cmds = append(cmds, m.handleCrawl(msg))
 
@@ -560,6 +593,7 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			m.containers.SetError(msg.err)
 		} else {
 			m.cache.containers[msg.key] = entry[[]provider.Container]{msg.items, m.now()}
+			m.cacheDirty = true
 			m.containers.SetItems(m.starredContainersFirst(msg.items))
 		}
 
@@ -580,6 +614,7 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 				msg.key = m.rebind(*msg.bound)
 			}
 			m.cache.objects[msg.key] = entry[[]provider.Object]{msg.items, m.now()}
+			m.cacheDirty = true
 			if m.versionsOf != nil {
 				m.setVersions(msg.items)
 			} else {
@@ -609,6 +644,7 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		// Errors and unsupported providers just leave the count out.
 		if msg.err == nil {
 			m.cache.objects[msg.key] = entry[[]provider.Object]{msg.items, m.now()}
+			m.cacheDirty = true
 			m.detail.SetVersions(msg.id, msg.items)
 		}
 
@@ -622,6 +658,7 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			m.detail.SetDescribeError(msg.err)
 		} else {
 			m.cache.details[msg.key] = entry[provider.Object]{msg.obj, m.now()}
+			m.cacheDirty = true
 			m.detail.SetDescribed(msg.obj)
 		}
 
@@ -1213,6 +1250,9 @@ func (m *Model) handleSources(msg sourcesMsg) tea.Cmd {
 	}
 	m.sourcesPending--
 	m.sourceResults[msg.provider] = msg
+	if msg.err == nil {
+		m.sourcesAt[msg.provider], m.cacheDirty = m.now(), true
+	}
 
 	var errs []string
 	for _, p := range m.providers {