feat: add compositor-agnostic window info utilities

- active-window: Get focused window info (class, pid) for Niri/Hyprland
- active-path: Get CWD of focused terminal window

These utilities abstract compositor-specific APIs for use in scripts.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

packages/active-path/active-path

@@ -0,0 +1,116 @@
+#!/usr/bin/env bash
+# active-path <pid>
+#
+# Given a PID (e.g. from active-window), output the active working directory
+# or project root for that process. Handles:
+#   - VSCode/Electron: parses --folder-uri from the process tree
+#   - Terminals (kitty, etc.): finds the deepest meaningful cwd in the tree
+#   - Fallback: own cwd
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+PID="${1:?Usage: active-path <pid>}"
+
+PROJECT_MARKERS=(.git Cargo.toml package.json Gemfile pyproject.toml go.mod flake.nix)
+
+# Walk up from a path looking for a project root marker.
+# Returns the marker directory, or the original path if nothing is found.
+find_project_root() {
+  local dir="$1"
+  local d="$dir"
+  while [[ "$d" != "/" && -n "$d" ]]; do
+    for marker in "${PROJECT_MARKERS[@]}"; do
+      [[ -e "$d/$marker" ]] && { printf '%s\n' "$d"; return 0; }
+    done
+    d="$(dirname "$d")"
+  done
+  printf '%s\n' "$dir"
+}
+
+# Decode a percent-encoded URI path component (file:/// paths are rarely
+# exotic, but spaces and non-ASCII chars do occur).
+url_decode() {
+  printf '%b' "${1//%/\\x}"
+}
+
+# Read null-terminated argv of a pid and look for --folder-uri.
+# Prints the decoded path and returns 0 if found, else returns 1.
+folder_uri_from_cmdline() {
+  local pid="$1"
+  local prev=""
+  while IFS= read -r -d $'\0' arg; do
+    case "$arg" in
+      --folder-uri=file://*)
+        url_decode "${arg#--folder-uri=file://}"
+        return 0
+        ;;
+      file://*)
+        if [[ "$prev" == "--folder-uri" ]]; then
+          url_decode "${arg#file://}"
+          return 0
+        fi
+        ;;
+    esac
+    prev="$arg"
+  done < "/proc/$pid/cmdline" 2>/dev/null
+  return 1
+}
+
+# Collect PIDs of all processes in the subtree rooted at $1.
+all_pids() {
+  local pid="$1"
+  printf '%s\n' "$pid"
+  for child in $(pgrep -P "$pid" 2>/dev/null); do
+    all_pids "$child"
+  done
+}
+
+# Given a list of PIDs, return the most specific (longest) cwd that lives
+# under the user's home directory.  Falls back to any non-root, non-proc cwd.
+best_cwd_from_pids() {
+  local best=""
+  for pid in "$@"; do
+    local cwd
+    cwd=$(readlink -f "/proc/$pid/cwd" 2>/dev/null) || continue
+    [[ "$cwd" == "/" || "$cwd" == "/root" || "$cwd" == "${HOME}" ]] && continue
+    [[ "$cwd" =~ ^/(proc|sys|run|dev) ]] && continue
+
+    # Prefer paths under home; among those prefer longer (more specific) ones
+    if [[ "$cwd" == "${HOME}"/* ]]; then
+      if [[ -z "$best" || "${#cwd}" -gt "${#best}" ]]; then
+        best="$cwd"
+      fi
+    elif [[ -z "$best" ]]; then
+      best="$cwd"
+    fi
+  done
+  [[ -n "$best" ]] && printf '%s\n' "$best"
+}
+
+# --- Main ---
+
+readarray -t TREE < <(all_pids "$PID")
+
+# 1. VSCode / Electron: search entire process tree for --folder-uri
+for pid in "${TREE[@]}"; do
+  if path=$(folder_uri_from_cmdline "$pid" 2>/dev/null); then
+    find_project_root "$path"
+    exit 0
+  fi
+done
+
+# 2. Terminal / generic: find the best cwd among all processes in the tree
+#    (prefers the shell or its running child over the terminal emulator itself,
+#    because terminal emulators typically sit at $HOME while the shell has moved)
+if cwd=$(best_cwd_from_pids "${TREE[@]}"); then
+  find_project_root "$cwd"
+  exit 0
+fi
+
+# 3. Absolute fallback: own cwd, even if it's /
+own=$(readlink -f "/proc/$PID/cwd" 2>/dev/null || true)
+[[ -n "$own" ]] && find_project_root "$own" && exit 0
+
+exit 1

packages/active-path/package.nix

@@ -0,0 +1,6 @@
+{pkgs, ...}:
+pkgs.writeShellApplication {
+  name = "active-path";
+  runtimeInputs = [pkgs.procps];
+  text = builtins.readFile ./active-path;
+}

packages/active-window/package.nix

@@ -0,0 +1,19 @@
+{pkgs, ...}:
+pkgs.writeShellApplication {
+  name = "active-window";
+  runtimeInputs = [pkgs.jq];
+  text = ''
+    if [[ -n "''${NIRI_SOCKET:-}" ]]; then
+      FOCUSED_ID=$(niri msg --json focused-window | jq '.id')
+      niri msg --json windows \
+        | jq --argjson id "$FOCUSED_ID" \
+             '[.[] | select(.id == $id)] | first
+              | {compositor: "niri", class: .app_id, pid: .pid}'
+    elif [[ -n "''${HYPRLAND_INSTANCE_SIGNATURE:-}" ]]; then
+      hyprctl activewindow -j \
+        | jq '{compositor: "hyprland", class: .class, pid: .pid}'
+    else
+      printf '{"compositor":"unknown","class":null,"pid":null}\n'
+    fi
+  '';
+}