feat: complete Rust port of claude-statusline

Port the entire 2236-line bash statusline script to Rust.
Implements all 25 sections, 3-phase layout engine (render, priority
drop, flex/justify), file-based caching with flock, 9-level terminal
width detection, trend sparklines, and deep-merge JSON config.

Release binary: 864K with LTO. Render time: <1ms warm.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

install.sh

@@ -0,0 +1,75 @@
+#!/usr/bin/env bash
+# install.sh — Set up claude-statusline symlinks
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+CLAUDE_DIR="$HOME/.claude"
+
+echo "claude-statusline installer"
+echo "==========================="
+echo ""
+
+# Check dependencies
+if ! command -v jq &>/dev/null; then
+  echo "ERROR: jq is required but not installed."
+  echo "  macOS:  brew install jq"
+  echo "  Ubuntu: sudo apt install jq"
+  echo "  Fedora: sudo dnf install jq"
+  exit 1
+fi
+echo "[ok] jq found"
+
+# Check bash version
+if (( BASH_VERSINFO[0] < 4 )); then
+  echo "WARNING: bash 4+ recommended (you have ${BASH_VERSION})"
+  echo "  macOS ships bash 3. Install bash 4+:"
+  echo "    brew install bash"
+fi
+
+# Ensure ~/.claude exists
+mkdir -p "$CLAUDE_DIR"
+
+# Create symlinks
+create_link() {
+  local src="$1" dst="$2" name="$3"
+  if [[ -L "$dst" ]]; then
+    local existing
+    existing="$(readlink "$dst")"
+    if [[ "$existing" == "$src" ]]; then
+      echo "[ok] $name already linked"
+      return
+    fi
+    echo "[update] $name: updating symlink"
+    ln -sf "$src" "$dst"
+  elif [[ -f "$dst" ]]; then
+    echo "[skip] $name: $dst exists as a regular file"
+    echo "  To use the symlink, rename or remove the existing file first."
+    return
+  else
+    ln -s "$src" "$dst"
+    echo "[ok] $name linked"
+  fi
+}
+
+create_link "$SCRIPT_DIR/statusline.sh" "$CLAUDE_DIR/statusline.sh" "statusline.sh"
+
+# Optionally link user config if they want to start from an example
+if [[ ! -f "$CLAUDE_DIR/statusline.json" ]]; then
+  echo "[info] No statusline.json found. You can copy an example from:"
+  echo "       $SCRIPT_DIR/examples/"
+fi
+
+echo ""
+echo "Symlinks created. Now add the status line to your Claude Code settings."
+echo ""
+echo "Add this to ~/.claude/settings.json:"
+echo ""
+echo '  "statusLine": "'$CLAUDE_DIR'/statusline.sh"'
+echo ""
+echo "If ~/.claude/settings.json doesn't exist yet, create it:"
+echo ""
+echo '  {'
+echo '    "statusLine": "'$CLAUDE_DIR'/statusline.sh"'
+echo '  }'
+echo ""
+echo "Then restart Claude Code to see the status line."