Initial release: Go Jdenticon library v0.1.0

- Core library with SVG and PNG generation
- CLI tool with generate and batch commands
- Cross-platform path handling for Windows compatibility
- Comprehensive test suite with integration tests

internal/engine/doc.go

@@ -0,0 +1,51 @@
+/*
+Package engine contains the core, format-agnostic logic for generating Jdenticon
+identicons. It is responsible for translating an input hash into a structured,
+intermediate representation of the final image.
+
+This package is internal to the jdenticon library and its API is not guaranteed
+to be stable. Do not use it directly.
+
+# Architectural Overview
+
+The generation process follows a clear pipeline:
+
+ 1. Hashing: An input value (e.g., a username) is hashed into a byte slice. This
+    is handled by the public `jdenticon` package.
+
+ 2. Generator: The `Generator` struct is the heart of the engine. It consumes the
+    hash to deterministically select shapes, colors, and their transformations
+    (rotation, position).
+
+ 3. Shape Selection: Based on bytes from the hash, specific shapes are chosen from
+    the predefined shape catalog in `shapes.go`.
+
+ 4. Transform & Positioning: The `transform.go` file defines how shapes are
+    positioned and rotated within the icon's grid. The center shape is
+    handled separately from the outer shapes.
+
+ 5. Colorization: `color.go` uses the hash and the `Config` to determine the
+    final hue, saturation, and lightness of the icon's foreground color.
+
+The output of this engine is a `[]RenderedElement`, which is a list of
+geometries and their associated colors. This intermediate representation is then
+passed to a renderer (see the `internal/renderer` package) to produce the final
+output (e.g., SVG or PNG). This separation of concerns allows the core generation
+logic to remain independent of the output format.
+
+# Key Components
+
+- generator.go: Main generation algorithm and core deterministic logic
+- shapes.go: Shape definitions and rendering with coordinate transformations
+- color.go: Color theme generation using HSL color space
+- config.go: Internal configuration structures and validation
+- transform.go: Coordinate transformation utilities
+
+# Hash-Based Determinism
+
+The engine ensures deterministic output by using specific positions within the
+input hash to drive shape selection, color generation, and transformations.
+This guarantees that identical inputs always produce identical identicons while
+maintaining visual variety across different inputs.
+*/
+package engine