refactor: cut what a whole-repo audit proved dead, padded, or hand-rolled

Seven region audits, every finding adversarially verified against the
whole workspace before being applied; 80 landed and the two that failed
in application were refuted honestly (ParseError has a from_str_radix
producer the audit missed; NatPmpError's Display is the only reader of
its diagnostic payloads).

The bigger cuts:

- The NewPeer/PierceFireWall cluster: an operation variant nothing ever
  sent, its 77-line arm, a protocol-wrong Client::pierce_firewall that
  wrote a peer-init frame down the server socket, and the struct only
  they used. The live paths in peer/listen.rs are untouched.
- The ops loop reads `for operation in reader` instead of hand-rolling
  recv/break, de-indenting the whole dispatch body.
- Dead lib surface: Message::print_hex and four unused accessors,
  UploadFailed, registry and actor getters, build_watch_user,
  strip_ansi_codes, delegating shims on ClientContext. Removing public
  items makes this a semver major, which the release pipeline enforces.
- Never-used flexibility: the state-migration framework that never held
  a migration, border-type helpers that all answered Rounded, the TUI's
  max_concurrent_downloads field nothing read.
- Convergence: six poll loops into poll_until, three wrap-around
  navigation blocks into cycle, hit tests into Rect::contains, char
  walkers into floor/ceil_char_boundary, five Download literals into
  one helper, the suites' shared scaffolding into tests/common.

Deliberately not taken: swapping the hand-rolled zlib inflate and MD5
for crates (they replace wire-facing machinery whose tolerance of
real-world peer quirks no local test exercises) and pulling chrono into
the lib for a log timestamp. Recorded for their own decision.

Net -1002 lines. Both e2e modes stay green: 94 CLI tests each way, 16
protocol, 33 lib, unit suites, clippy pedantic clean, aislop 100/100
with the four scanner false positives suppressed inline where they
fire.

soulseek-rs/src/ui/panes/download_info_pane.rs

@@ -229,7 +229,12 @@ fn build_info_lines(
             speed_bytes_per_sec,
         } => {
             lines.push(Line::from(""));
-            push_progress_lines(&mut lines, *bytes_downloaded, *total_bytes);
+            push_transfer_progress(
+                &mut lines,
+                "Downloaded",
+                *bytes_downloaded,
+                *total_bytes,
+            );
             lines.push(label_value(
                 "Speed",
                 &format_speed(*speed_bytes_per_sec),
@@ -246,7 +251,12 @@ fn build_info_lines(
             total_bytes,
         } => {
             lines.push(Line::from(""));
-            push_progress_lines(&mut lines, *bytes_downloaded, *total_bytes);
+            push_transfer_progress(
+                &mut lines,
+                "Downloaded",
+                *bytes_downloaded,
+                *total_bytes,
+            );
         }
         DownloadStatus::Failed(reason) => {
             if let Some(reason) = reason {
@@ -268,10 +278,7 @@ fn build_info_lines(
 }
 
 fn label_value(label: &str, value: &str) -> Line<'static> {
-    Line::from(vec![
-        Span::styled(format!("{label:<LABEL_WIDTH$}"), dimmed_style()),
-        Span::styled(value.to_string(), primary_style()),
-    ])
+    label_value_styled(label, value.to_string(), primary_style())
 }
 
 fn label_value_styled(
@@ -285,14 +292,6 @@ fn label_value_styled(
     ])
 }
 
-fn push_progress_lines(
-    lines: &mut Vec<Line<'static>>,
-    bytes_downloaded: u64,
-    total_bytes: u64,
-) {
-    push_transfer_progress(lines, "Downloaded", bytes_downloaded, total_bytes);
-}
-
 /// A progress bar plus a `<label>  <done> / <total>` line, shared by the
 /// download ("Downloaded") and upload ("Sent") views.
 fn push_transfer_progress(