Initial: desk + ncantu placeholder + per-project cursor configs

**Motivations:**
- Centraliser les fichiers Cursor (rules, skills, agents, commands, hooks) par user et par projet

**Root causes:**
- N/A

**Correctifs:**
- N/A

**Evolutions:**
- desk: rules, skills-cursor, agents, commands, hooks, argv/hooks/mcp.json
- ncantu: README placeholder
- 4NK_node, algo, builazoo, ia_local, lecoffre_ng, lecoffre_ng_pprod, lecoffre_ng_test: .cursor contents

**Pages affectées:**
- cursor/desk/, cursor/ncantu/, cursor/<project>/

desk/hooks/post-tool-use-failure.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+# postToolUseFailure: log when a tool fails (shell, etc.)
+HOOKS_DIR="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=lib.sh
+. "${HOOKS_DIR}/lib.sh"
+
+input=$(cat)
+tool_name=$(echo "$input" | jq -r '.tool_name // "?"')
+failure_type=$(echo "$input" | jq -r '.failure_type // "?"')
+error_message=$(echo "$input" | jq -r '.error_message // ""')
+command=$(echo "$input" | jq -r '.tool_input.command // .tool_input // ""' 2>/dev/null || echo "")
+log_event "postToolUseFailure" "tool=$tool_name failure=$failure_type"
+log_json_truncated "postToolUseFailure_error" "$error_message" 500
+if [ -n "$command" ]; then
+  log_event "postToolUseFailure" "command=${command:0:150}"
+fi
+echo '{}'
+exit 0