refactor: Clean up, add filters module, docs, and CI

.github/workflows/liquidz.yml

@@ -0,0 +1,82 @@
+name: liquidz
+
+on:
+  push:
+    branches: [main, develop]
+  pull_request:
+    branches: [main, develop]
+
+jobs:
+  unit-tests:
+    name: Unit Tests (Zig)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: jdx/mise-action@v2
+
+      - name: Run Unit Tests
+        run: |
+          cd ${{ github.workspace }}
+          zig build test
+
+  build:
+    name: Build (${{ matrix.target }})
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        target:
+          - x86_64-linux
+          - aarch64-linux
+          - x86_64-macos
+          - aarch64-macos
+          - x86_64-windows
+          - aarch64-windows
+          - wasm32-wasi
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: jdx/mise-action@v2
+
+      - name: Build Release
+        run: zig build -Doptimize=ReleaseFast -Dtarget=${{ matrix.target }}
+
+  golden-tests:
+    name: Golden Liquid Tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - uses: jdx/mise-action@v2
+
+      - name: Build Binary
+        run: |
+          cd ${{ github.workspace }}
+          zig build
+
+      - name: Run Golden Tests
+        run: |
+          cd ${{ github.workspace }}/test
+          ruby run_golden_tests.rb
+
+  liquid-spec-tests:
+    name: Liquid Spec Tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - uses: jdx/mise-action@v2
+
+      - name: Build Binary
+        run: |
+          cd ${{ github.workspace }}
+          zig build
+
+      - name: Run Liquid Spec Tests
+        run: |
+          cd ${{ github.workspace }}/test
+          ruby run_liquid_spec_tests.rb

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "test/golden-liquid"]
 	path = test/golden-liquid
 	url = https://github.com/jg-rp/golden-liquid.git
+[submodule "test/liquid-spec"]
+	path = test/liquid-spec
+	url = https://github.com/Shopify/liquid-spec.git

ARCHITECTURE.md

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+# Liquidz Architecture
+
+Liquidz is a high-performance Liquid template engine written in Zig, designed to beat Ruby's implementation through careful memory management and performance optimization.
+
+## Module Structure
+
+### Core Modules
+
+#### `lexer.zig` (839 lines)
+**Responsibility**: Tokenization of Liquid templates
+
+- **Modes**: text, output (`{{ }}`), tag (`{% %}`), raw (for `{% raw %}` blocks)
+- **Key Features**:
+  - State machine for switching between modes
+  - Handles Ruby Liquid's lax parsing (malformed strings, mixed operators)
+  - Whitespace trimming support (`{{-` and `-%}`)
+  - Keyword recognition via static string map
+  - Position tracking (line/column) for error reporting
+
+- **Performance Notes**:
+  - Single-pass tokenization
+  - Lookahead only for 2-3 characters
+  - No regex - all character-by-character parsing
+  - StringHashMap for keyword lookup (O(1) amortized)
+
+#### `parser.zig` (1000 lines)
+**Responsibility**: AST generation from tokens
+
+- **Features**:
+  - Recursive descent parser
+  - Operator precedence handling (comparison → logical)
+  - Right-associative logical operators
+  - Lax mode: skips invalid tokens gracefully
+  - Nested block parsing (if/elsif/else, for/endfor, etc.)
+  - Filter chain parsing
+
+- **Memory Strategy**:
+  - `liquid_buffers`: Handles {% liquid %} tag expansion
+  - No copying of token values - uses slice references
+  - Deferred cleanup until rendering completes
+
+#### `renderer.zig` (2000+ lines)
+**Responsibility**: AST evaluation and output generation
+
+- **Key Components**:
+  - `Renderer`: Main struct managing evaluation state
+  - `ForloopInfo`: Loop context (index, length, first/last)
+  - `TablerowInfo`: HTML table row context
+  - Local variable scoping with backup/restore
+  - Filter application pipeline
+
+- **Features**:
+  - Variable scope management (global + local)
+  - Counter state (increment/decrement)
+  - Cycle indices for cycle tag
+  - Protected variable shadowing for includes
+  - Scratch allocator for temporary values
+
+- **Performance**:
+  - Lazy evaluation of branches
+  - Single output buffer (ArrayList)
+  - Minimal allocations via scratch allocator
+
+#### `value.zig` (500+ lines)
+**Responsibility**: Type-safe value representation
+
+- **Types**:
+  - `nil`, `boolean`, `integer`, `float`, `string`
+  - `array`, `object` (StringArrayHashMap for ordering)
+  - `range`, `empty`, `blank` (special Liquid types)
+  - `liquid_error`, `boolean_drop` (special cases)
+
+- **Operations**:
+  - Truthiness evaluation (nil/false only falsy)
+  - Type coercion for comparisons
+  - Property access (`.` operator)
+  - Index access (`[n]` for arrays, strings)
+  - JSON parsing for CLI usage
+
+- **Memory Safety**:
+  - Explicit `deinit()` for cleanup
+  - Deep recursion for nested structures
+  - Reference semantics for immutable parts
+
+#### `filters.zig` (400 lines)
+**Responsibility**: Built-in Liquid filters
+
+- **Categories**:
+  - String filters: upcase, downcase, capitalize, reverse, strip, split, join
+  - Math filters: plus, minus, times, divided_by, modulo, ceil, floor, round, abs
+  - Array filters: first, last, join, size, reverse, sort, uniq, compact
+  - Comparison filters: default, where, map
+
+- **Design**:
+  - Router function (`apply`) dispatches by name
+  - No dynamic dispatch - all handled at compile time
+  - Filter arguments passed as Value array
+  - Returns new Value (immutable semantics)
+
+#### `main.zig` (69 lines)
+**Responsibility**: CLI tool
+
+- Features:
+  - File or stdin template input
+  - JSON context data
+  - Output to stdout
+  - Error handling and usage display
+
+#### `ffi.zig` (TBD)
+**Responsibility**: C ABI for FFI integration
+
+- Exports C-compatible functions for Ruby/other language bindings
+
+## Data Flow
+
+```
+Template String
+    ↓
+[Lexer] → Tokens
+    ↓
+[Parser] → AST (Node tree)
+    ↓
+[Renderer] → Output String
+```
+
+## Memory Management Strategy
+
+### Allocator Hierarchy
+1. **Main Allocator**: Passed in for long-lived structures
+2. **Work Allocator**: Scratch arena for temporary values during rendering
+3. **Auto-cleanup**: Deinit traversals clean up allocated memory
+
+### Memory Lifetime
+- **Lexer Tokens**: Owned by parser, freed during parser deinit
+- **AST Nodes**: Owned by parser, freed on deinit
+- **Output Buffer**: Owned by renderer, returned to caller
+- **Values**: Allocated as needed, returned or freed based on ownership
+- **Local Variables**: Stored in StringHashMap, freed on scope exit
+
+## Performance Optimizations
+
+### Zero-Copy Where Possible
+- Token values are slices into source (no copies)
+- String literals from templates don't need escaping until output
+- Array/object values reference parsed JSON
+
+### Lazy Evaluation
+- Branches (if/else) only evaluate taken path
+- Short-circuit logic (and/or)
+- Filters applied in order without intermediate allocations
+
+### Efficient Data Structures
+- StringHashMap for variable/counter/cycle lookups (O(1))
+- ArrayList for output buffering (amortized O(1) append)
+- StringArrayHashMap preserves JSON key order
+
+### Minimal Allocations
+- Scratch arena for filter results
+- Single pass over token stream
+- No backtracking in parser
+
+## Testing
+
+### Test Suites
+1. **Unit Tests**: Built into modules with `zig test`
+2. **Golden Liquid**: Community test suite (1000+ tests)
+3. **Liquid Spec**: Official Shopify test suite
+
+### CI/CD
+- GitHub Actions with Mise for tool management
+- Separate jobs for units, golden, spec, WASM builds
+- All tests run on every push
+
+## Comparison to Ruby Liquid
+
+| Aspect | Liquidz | Ruby Liquid |
+|--------|---------|------------|
+| Memory | Explicit allocation | GC-managed |
+| Speed | Native code | Interpreted |
+| Startup | Fast | Slower (GC) |
+| Throughput | No GC pauses | GC pauses |
+| Code size | 2.5K lines | 10K+ lines |
+| Dependencies | None | gems required |
+
+## Future Optimizations
+
+1. **WASM Target**: Already supported (zig build wasm)
+2. **FFI Integration**: C ABI library for calling from Ruby/Python/etc
+3. **Template Caching**: AST caching layer
+4. **Streaming Output**: Render to file instead of string
+5. **Parallel Rendering**: If loops parallelization