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/styles.rs

@@ -1,5 +1,4 @@
 // Reusable styles and colors for consistent UI appearance
-#![allow(dead_code)]
 
 use ratatui::style::{Color, Modifier, Style};
 use ratatui::text::{Line, Span};
@@ -103,14 +102,6 @@ pub fn unfocused_border_style() -> Style {
     Style::default().fg(DUST)
 }
 
-pub const fn focused_border_type() -> BorderType {
-    BorderType::Rounded
-}
-
-pub const fn unfocused_border_type() -> BorderType {
-    BorderType::Rounded
-}
-
 pub fn border_style(focused: bool) -> Style {
     if focused {
         focused_border_style()
@@ -119,14 +110,6 @@ pub fn border_style(focused: bool) -> Style {
     }
 }
 
-pub const fn border_type(focused: bool) -> BorderType {
-    if focused {
-        focused_border_type()
-    } else {
-        unfocused_border_type()
-    }
-}
-
 pub fn title_style(focused: bool) -> Style {
     if focused {
         Style::default().fg(PHOSPHOR).add_modifier(Modifier::BOLD)
@@ -159,7 +142,7 @@ pub fn pane_block(focused: bool) -> Block<'static> {
     Block::default()
         .borders(Borders::ALL)
         .border_style(border_style(focused))
-        .border_type(border_type(focused))
+        .border_type(BorderType::Rounded)
         .padding(PANE_PADDING)
 }