perf(roadmap): hoist readdirSync out of phase loop in analyze command (#1899)

cmdRoadmapAnalyze called fs.readdirSync(phasesDir) inside the
per-phase while loop, causing O(N^2) directory reads for N phases.
At 50 phases this produced 100 redundant syscalls; at 100 phases, 200.

Move the directory listing before the loop and build a lookup array
that is reused for each phase match. This reduces the pattern from
O(N^2) to O(N) directory reads.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

get-shit-done/bin/lib/roadmap.cjs

@@ -129,6 +129,15 @@ function cmdRoadmapAnalyze(cwd, raw) {
   const phases = [];
   let match;
 
+  // Build phase directory lookup once (O(1) readdir instead of O(N) per phase)
+  const _phaseDirNames = (() => {
+    try {
+      return fs.readdirSync(phasesDir, { withFileTypes: true })
+        .filter(e => e.isDirectory())
+        .map(e => e.name);
+    } catch { return []; }
+  })();
+
   while ((match = phasePattern.exec(content)) !== null) {
     const phaseNum = match[1];
     const phaseName = match[2].replace(/\(INSERTED\)/i, '').trim();
@@ -155,9 +164,7 @@ function cmdRoadmapAnalyze(cwd, raw) {
     let hasResearch = false;
 
     try {
-      const entries = fs.readdirSync(phasesDir, { withFileTypes: true });
-      const dirs = entries.filter(e => e.isDirectory()).map(e => e.name);
-      const dirMatch = dirs.find(d => phaseTokenMatches(d, normalized));
+      const dirMatch = _phaseDirNames.find(d => phaseTokenMatches(d, normalized));
 
       if (dirMatch) {
         const phaseFiles = fs.readdirSync(path.join(phasesDir, dirMatch));