feat: the changelog in the status pane, built in (#12)

The status pane's rows (`0`, then `enter`) end with the changelog: every release up to the running one, newest first.

```
v0.2.0     2026-10-12
           added: Search with fzf's scoring and query syntax (#11) (65dc2d7)
           fixed: …
v0.1.0     2026-10-10
           Hello world 👋
```

- `CHANGELOG.md` is embedded at build time by a small root package (`changelog.go`, `package lazysecrets`, `//go:embed`), so it needs no network and matches the binary. `release.sh` updates the file before tagging, so a release's binary includes its own entry. `go install …@latest` gets it too, since the module includes the file.
- Entries show as text: links become `(#11) (65dc2d7)` (`update.PlainLinks`, shared with the `U` notes). `/` filters them like any Fields pane (`/fixed`, `/search`), and `y` copies one.
- `cliff.toml`: #11 was squash-merged with #10 (the status pane) in it, so a preprocessor rewrites its entry to name both. Otherwise the status pane would be missing from the changelog.

Test for the parsing: versions and dates, kinds, links as text, a release's own words, and the header and footer left out.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>
Reviewed-on: #12

internal/update/update.go

@@ -50,9 +50,12 @@ type Release struct {
 // every release ends with.
 func (r Release) Notes() string {
 	notes, _, _ := strings.Cut(r.Body, "## Install")
-	return mdLink.ReplaceAllString(strings.TrimSpace(notes), "$1")
+	return PlainLinks(strings.TrimSpace(notes))
 }
 
+// PlainLinks shows Markdown links as their text, for a terminal.
+func PlainLinks(s string) string { return mdLink.ReplaceAllString(s, "$1") }
+
 // mdLink is a Markdown link, [text](url): the notes link PRs and commits,
 // and a terminal shows them as their text.
 var mdLink = regexp.MustCompile(`\[([^\]]+)\]\((https?://[^)\s]+)\)`)