Fix menubar showing empty data after reboot when CLI is installed via fnm/nvm

Login-item launches don't source .zshrc, leaving version-manager bin
directories (fnm, nvm, volta, asdf) absent from PATH. The menubar's
augmentedPath only covered /opt/homebrew/bin and /usr/local/bin, so
codeburn was never found after a cold reboot.

- Add discoverNodeManagerBinDirs() that dynamically scans for fnm, nvm,
  volta, and asdf installations and adds the latest Node version's bin
  directory to PATH
- Add PATH logging to DataClient spawn error for easier future diagnosis
- Log the swallowed error in hydrateCache() catch block so silent
  cache-empty failures are visible in stderr
- Add scripts/diagnose-menubar-cli.sh for testing restricted-PATH CLI
  execution without rebuilding the menubar app

scripts/diagnose-menubar-cli.sh

@@ -0,0 +1,73 @@
+#!/bin/bash
+# Replicates the menubar's restricted PATH environment to test if the CLI
+# can find and run codeburn with the same PATH the menubar provides.
+#
+# The menubar augments PATH with: /opt/homebrew/bin /usr/local/bin
+# The base PATH for a Login Item is typically: /usr/bin:/bin:/usr/sbin:/sbin
+
+set -euo pipefail
+
+RESTRICTED_PATH="/usr/bin:/bin:/usr/sbin:/sbin:/opt/homebrew/bin:/usr/local/bin"
+
+echo "=== Menubar PATH Diagnostic ==="
+echo ""
+echo "Using restricted PATH: $RESTRICTED_PATH"
+echo ""
+
+# 1. Check if codeburn is found
+echo "--- Step 1: Locate codeburn binary ---"
+FOUND=$(PATH="$RESTRICTED_PATH" /usr/bin/env which codeburn 2>&1 || true)
+if [ -z "$FOUND" ]; then
+    echo "FAIL: codeburn not found in restricted PATH"
+    echo ""
+    echo "Where codeburn actually is:"
+    /usr/bin/env which -a codeburn 2>/dev/null || echo "(not found anywhere)"
+    echo ""
+    echo "Fix: codeburn is installed outside the menubar's PATH. Options:"
+    echo "  1. Add the install directory to CodeburnCLI.additionalPathEntries"
+    echo "  2. Symlink codeburn into /usr/local/bin"
+    exit 1
+fi
+echo "OK: codeburn found at: $FOUND"
+echo ""
+
+# 2. Check if node is found (needed for codeburn shell wrapper)
+echo "--- Step 2: Locate node binary ---"
+NODE_FOUND=$(PATH="$RESTRICTED_PATH" /usr/bin/env which node 2>&1 || true)
+if [ -z "$NODE_FOUND" ]; then
+    echo "WARNING: node not found in restricted PATH"
+    echo "This may cause codeburn to fail if it's a shell wrapper."
+    echo ""
+else
+    echo "OK: node found at: $NODE_FOUND"
+    echo "Node version: $(PATH="$RESTRICTED_PATH" node --version 2>&1 || echo 'failed')"
+fi
+echo ""
+
+# 3. Run the command the menubar spawns
+echo "--- Step 3: Run menubar-equivalent CLI command ---"
+echo "Command: codeburn status --format menubar-json --period today --provider all"
+echo ""
+
+STDERR_FILE=$(mktemp)
+trap 'rm -f "$STDERR_FILE"' EXIT
+
+if PATH="$RESTRICTED_PATH" /usr/bin/env -- codeburn status --format menubar-json --period today --provider all 2>"$STDERR_FILE"; then
+    echo ""
+    if [ -s "$STDERR_FILE" ]; then
+        echo "Warnings/errors on stderr:"
+        cat "$STDERR_FILE"
+    fi
+    echo ""
+    echo "SUCCESS: CLI ran successfully with restricted PATH."
+else
+    EXIT_CODE=$?
+    echo ""
+    echo "FAIL: CLI exited with code $EXIT_CODE"
+    if [ -s "$STDERR_FILE" ]; then
+        echo ""
+        echo "Stderr output:"
+        cat "$STDERR_FILE"
+    fi
+    exit 1
+fi