Add beginner guide, LLM guardrails disclosure, fix bugs

- Add docs/GETTING-STARTED.md for non-technical users
- Add "Known Limitations" section to README about LLM safety guardrails
- Add FAQ entry about AI seeming evasive on trauma topics
- Fix setup.sh prompt_choice outputting to stdout instead of stderr
- Fix first session detection in CLAUDE.template.md (check for empty
  sessions folder before trying to reference previous sessions)
- Add guardrails acknowledgment instructions to CLAUDE.template.md
  (AI should be honest when hitting built-in limitations)

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

setup.sh

@@ -54,7 +54,7 @@ prompt_choice() {
     local default="$2"
     local result
 
-    echo -ne "${prompt} [${default}]: "
+    echo -ne "${prompt} [${default}]: " >&2
     read -r result
     echo "${result:-$default}"
 }
@@ -64,7 +64,7 @@ prompt_yes_no() {
     local default="$2"
     local result
 
-    echo -ne "${prompt} [${default}]: "
+    echo -ne "${prompt} [${default}]: " >&2
     read -r result
     result="${result:-$default}"
     [[ "$result" =~ ^[Yy] ]]