fix(core): add --no-index to isGitIgnored for tracked file detection (#703)

Without --no-index, git check-ignore only reports files as ignored if
they are untracked. Once .planning/ files enter git's index (e.g., from
an initial commit before .gitignore was set up), check-ignore returns
"not ignored" even when .gitignore explicitly lists .planning/.

This means the documented safety net — "if .planning/ is gitignored,
commit_docs is automatically false" — silently fails for any repo where
.planning/ was ever committed. The --no-index flag checks .gitignore
rules regardless of tracking state, matching user expectations.

Closes #703

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

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

@@ -124,7 +124,11 @@ function loadConfig(cwd) {
 
 function isGitIgnored(cwd, targetPath) {
   try {
-    execSync('git check-ignore -q -- ' + targetPath.replace(/[^a-zA-Z0-9._\-/]/g, ''), {
+    // --no-index checks .gitignore rules regardless of whether the file is tracked.
+    // Without it, git check-ignore returns "not ignored" for tracked files even when
+    // .gitignore explicitly lists them — a common source of confusion when .planning/
+    // was committed before being added to .gitignore.
+    execSync('git check-ignore -q --no-index -- ' + targetPath.replace(/[^a-zA-Z0-9._\-/]/g, ''), {
       cwd,
       stdio: 'pipe',
     });