Add per-session claude token/cost usage panel (WSL, v1)

Reads ~/.claude/projects/*.jsonl transcripts from the open WSL panes'
distros and shows per-session token counts + estimated USD cost, with a
running total in the titlebar.

Backend (src-tauri/src/usage.rs): new get_claude_usage command. For each
distro it probes $HOME once via wsl.exe, reaches the transcripts over the
\\wsl.localhost UNC share, and tallies message.usage per model per
session (summed by each line's model, since a session can switch models).
Results cached by (path,size,mtime) so polling only re-parses the file
that grew; recency-capped (30d / 50 sessions) to bound scan cost.
Windows-only; returns [] elsewhere. quiet_command made pub(crate).

Frontend: src/lib/usage.ts holds the pricing table (per-MTok rates,
matched by model-family substring) + cost/format helpers, so rates are
editable without recompiling Rust. UsagePanel.tsx mirrors the MCP panel
modal; rows whose transcript cwd matches an open pane are highlighted
with a [pane: label] tag. App polls every 20s (visible windows) for the
titlebar 💰 total and every 5s while the panel is open. Ctrl+Shift+U
opens it; added to shortcuts.ts + regenerated README.

tsc clean. Rust builds on the Windows host; needs runtime verification.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src-tauri/src/pty.rs

@@ -495,7 +495,7 @@ fn looks_like_password_prompt(buf: &[u8]) -> bool {
 // ---- distro enumeration -----------------------------------------------------
 
 /// Run a process without flashing a console window on Windows.
-fn quiet_command(program: &str) -> std::process::Command {
+pub(crate) fn quiet_command(program: &str) -> std::process::Command {
     let mut c = std::process::Command::new(program);
     #[cfg(windows)]
     {