feat: implement module system foundation (parser + resolver)

[Copilot]

Implements Phases 1-2 of the Shortcake module system per docs/MODULES.md: parser extensions and module resolution infrastructure.

Parser Extensions

• mod keyword: New token type, AST node (mod_decl), and parsing logic
• AST support: mod_info struct (module_name, file_path, is_main) with proper memory management
• Import paths: Existing dotted path support (utils.math) works with new module system

Module Resolver

New src/module_resolver.zig provides:

• Path resolution: utils.math → utils/math.sho
• Search paths: Multi-directory module lookup
• Circular imports: DFS-based detection (direct and indirect cycles)
• Module cache: Avoid redundant parsing
• Dependency tracking: Import graph for validation

var resolver = ModuleResolver.init(allocator);
try resolver.addSearchPath("/project/modules");
const file_path = try resolver.resolveModule("utils.math");  // → /project/modules/utils/math.sho

// Circular import detection
try resolver.addDependency("a", "b");
try resolver.addDependency("b", "a");
const circular = try resolver.detectCircularImports("a", &stack);  // → true

Example Module

mod

fn add(a: i32, b: i32): i32 = a + b

mod

import utils.math

fn main() do
  result = utils.math.add(5, 3)
end

Changes

• src/parser.zig: parseModDecl(), mod_kw token recognition
• src/ast.zig: mod_decl node type, setModInfo() helper
• src/module_resolver.zig: New (370 lines)
• test/test_module_parsing.zig: New - parser tests
• test/test_module_resolver.zig: New - 10+ resolver tests
• build.zig: Module registration

Next: Symbol resolution (import tracking, cross-module references)

Total: ~930 lines (implementation + tests)

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/igorgue/shortcake/git/blobs/b609b3bc9890080ef4b7c1b1932209f194dc061e
  • Triggering command: `python3 -c
    import urllib.request
    import json
    import base64

url = 'REDACTED'
req = urllib.request.Request(url)
req.add_header('Accept', 'application/vnd.github.v3+json')

with urllib.request.urlopen(req) as response:
data = json.loads(response.read())
content = base64.b64decode(data['content']).decode('utf-8')
print(content)` (http block)

• ziglang.org
  • Triggering command: wget -q REDACTED (dns block)
  • Triggering command: curl -sL REDACTED (dns block)
  • Triggering command: wget REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Module System v0</issue_title>
<issue_description>Implement the module system in Shortcake. Following the plan from docs/MODULES.md</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Module System v0 #1

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