docs: add user guide and example projects (#139)

New users were confused about which files they write vs. which Ralph
manages, and how PROMPT.md, specs/, and fix_plan.md relate to each other.

Added:
- docs/user-guide/ with quick start tutorial, file reference, and
  requirements writing guide
- examples/simple-cli-tool/ showing minimal Ralph configuration
- examples/rest-api/ demonstrating when to use specs/
- README section explaining Ralph files and their relationships

Also documents specs/stdlib/ purpose for reusable patterns.

examples/simple-cli-tool/.ralph/fix_plan.md

@@ -0,0 +1,22 @@
+# Fix Plan - Todo CLI
+
+## Priority 1: Foundation
+- [ ] Set up package.json with commander and jest dependencies
+- [ ] Create src/storage.js with load/save functions for ~/.todos.json
+- [ ] Create src/index.js entry point with commander setup
+
+## Priority 2: Core Commands
+- [ ] Implement `todo add "description"` command
+- [ ] Implement `todo list` command with status indicators
+- [ ] Implement `todo complete <id>` command
+- [ ] Implement `todo delete <id>` command
+
+## Priority 3: Polish
+- [ ] Add comprehensive --help text for each command
+- [ ] Handle edge cases (empty list, invalid ID, negative ID)
+- [ ] Write unit tests for storage.js module
+- [ ] Write integration tests for CLI commands
+- [ ] Add a `todo clear` command to remove all completed tasks
+
+## Discovered
+<!-- Ralph will add discovered tasks here -->