Fix GitHub Actions workflow failures

- Reorganize examples into subdirectories (basic/, adaptive/)
  - Each example now has its own directory with main.go
  - Prevents 'multiple main() declarations' build errors
- Remove examples/indexed_engine.go (library code, not a runnable example)
- Update CI workflow:
  - Remove go.sum verification (project has no external dependencies)
  - Fix build step to handle new examples structure
  - Build each example in its own directory
- Add examples/README.md documenting the new structure

This fixes all build, lint, and format check failures in GitHub Actions.

Author: leifj

.github/workflows/ci.yml

@@ -96,10 +96,10 @@ jobs:
           exit 1
         fi
     
-    - name: Verify go.mod and go.sum
+    - name: Verify go.mod
       run: |
         go mod tidy
-        git diff --exit-code go.mod go.sum
+        git diff --exit-code go.mod
 
   build:
     name: Build
@@ -114,21 +114,26 @@ jobs:
       with:
         go-version: '1.25.x'
 
-    - name: Build
-      run: go build -v ./...
+    - name: Build main package
+      run: go build -v .
+    
+    - name: Build sub-packages
+      run: go build -v ./pkg/...
 
     - name: Build examples
       run: |
-        for example in examples/*.go; do
-          if [ -f "$example" ]; then
-            go build -v "$example"
+        for example_dir in examples/*/; do
+          if [ -d "$example_dir" ]; then
+            echo "Building $example_dir"
+            (cd "$example_dir" && go build -v .)
           fi
         done
     
     - name: Build commands
       run: |
         for cmd in cmd/*; do
           if [ -d "$cmd" ]; then
+            echo "Building $cmd"
             go build -v "./$cmd"
           fi
         done

examples/README.md

@@ -0,0 +1,53 @@
+# SPOCP Examples
+
+This directory contains runnable examples demonstrating various features of the SPOCP library.
+
+## Available Examples
+
+### basic
+Basic usage example showing:
+- Creating an engine with `spocp.New()`
+- Adding rules
+- Querying policies
+- Using wildcards and sets
+
+Run with:
+```bash
+cd examples/basic
+go run main.go
+```
+
+### adaptive
+Demonstrates the AdaptiveEngine with automatic indexing:
+- Creating rules with diverse tags
+- Automatic indexing optimization
+- Performance statistics
+- Index transition monitoring
+
+Run with:
+```bash
+cd examples/adaptive
+go run main.go
+```
+
+## Building Examples
+
+Build all examples:
+```bash
+for example_dir in examples/*/; do
+  (cd "$example_dir" && go build .)
+done
+```
+
+Build a specific example:
+```bash
+cd examples/basic
+go build .
+```
+
+## Example Structure
+
+Each example is in its own subdirectory with a `main.go` file. This structure:
+- Allows each example to be built independently
+- Prevents conflicts between multiple `main()` functions
+- Makes it easy to add new examples