feat: add HTTP framework with routing and JSON helpers

- Add stdlib/http.lux with:
  - Response builders (httpOk, httpNotFound, etc.)
  - Path pattern matching with parameter extraction
  - JSON construction helpers (jsonStr, jsonNum, jsonObj, etc.)
- Add examples/http_api.lux demonstrating a complete REST API
- Add examples/http_router.lux showing the routing pattern
- Update stdlib/lib.lux to include http module

The framework provides functional building blocks for web apps:
- Route matching: pathMatches("/users/:id", path)
- Path params: getPathSegment(path, 1)
- Response building: httpOk(jsonObj(...))

Note: Due to current type system limitations with type aliases
and function types, the framework uses inline types rather
than abstract Request/Response types.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

stdlib/http.lux

@@ -0,0 +1,161 @@
+// HTTP Framework for Lux
+//
+// Provides helpers for building web applications.
+//
+// Note: Due to current type system limitations, this module provides
+// helper functions rather than abstract types. Use the HttpServer effect
+// directly for the server loop.
+
+// ============================================================
+// Response Builder Functions
+// ============================================================
+
+// Create a 200 OK response
+fn httpOk(body: String): { status: Int, body: String } =
+    { status: 200, body: body }
+
+// Create a 201 Created response
+fn httpCreated(body: String): { status: Int, body: String } =
+    { status: 201, body: body }
+
+// Create a 204 No Content response
+fn httpNoContent(): { status: Int, body: String } =
+    { status: 204, body: "" }
+
+// Create a 400 Bad Request response
+fn httpBadRequest(body: String): { status: Int, body: String } =
+    { status: 400, body: body }
+
+// Create a 401 Unauthorized response
+fn httpUnauthorized(body: String): { status: Int, body: String } =
+    { status: 401, body: body }
+
+// Create a 403 Forbidden response
+fn httpForbidden(body: String): { status: Int, body: String } =
+    { status: 403, body: body }
+
+// Create a 404 Not Found response
+fn httpNotFound(body: String): { status: Int, body: String } =
+    { status: 404, body: body }
+
+// Create a 500 Server Error response
+fn httpServerError(body: String): { status: Int, body: String } =
+    { status: 500, body: body }
+
+// ============================================================
+// Path Matching
+// ============================================================
+
+// Check if a path matches a pattern with wildcards
+// Pattern "/users/:id" matches "/users/42"
+fn pathMatches(path: String, pattern: String): Bool = {
+    let pathParts = String.split(path, "/")
+    let patternParts = String.split(pattern, "/")
+    if List.length(pathParts) != List.length(patternParts) then false
+    else matchPathParts(pathParts, patternParts)
+}
+
+fn matchPathParts(pathParts: List<String>, patternParts: List<String>): Bool = {
+    if List.length(pathParts) == 0 then true
+    else {
+        match List.head(pathParts) {
+            None => true,
+            Some(pathPart) => {
+                match List.head(patternParts) {
+                    None => true,
+                    Some(patternPart) => {
+                        let isMatch = if String.startsWith(patternPart, ":") then true else pathPart == patternPart
+                        if isMatch then {
+                            let restPath = Option.getOrElse(List.tail(pathParts), [])
+                            let restPattern = Option.getOrElse(List.tail(patternParts), [])
+                            matchPathParts(restPath, restPattern)
+                        } else false
+                    }
+                }
+            }
+        }
+    }
+}
+
+// Extract a path segment by position (0-indexed, skipping leading empty segment)
+// For path "/users/42", getPathSegment(path, 1) returns Some("42")
+fn getPathSegment(path: String, index: Int): Option<String> = {
+    let parts = String.split(path, "/")
+    List.get(parts, index + 1)
+}
+
+// ============================================================
+// JSON Helpers
+// ============================================================
+
+// Escape a string for JSON (handles quotes and backslashes)
+fn jsonEscape(s: String): String = {
+    String.replace(String.replace(s, "\\", "\\\\"), "\"", "\\\"")
+}
+
+// Create a JSON string field: "key": "value"
+fn jsonString(key: String, value: String): String = {
+    "\"" + jsonEscape(key) + "\":\"" + jsonEscape(value) + "\""
+}
+
+// Create a JSON number field: "key": 42
+fn jsonNumber(key: String, value: Int): String = {
+    "\"" + jsonEscape(key) + "\":" + toString(value)
+}
+
+// Create a JSON boolean field: "key": true
+fn jsonBool(key: String, value: Bool): String = {
+    let boolStr = if value then "true" else "false"
+    "\"" + jsonEscape(key) + "\":" + boolStr
+}
+
+// Wrap content in JSON object braces
+fn jsonObject(content: String): String =
+    "{" + content + "}"
+
+// Wrap content in JSON array brackets
+fn jsonArray(content: String): String =
+    "[" + content + "]"
+
+// Join multiple JSON fields/items with commas
+fn jsonJoin(items: List<String>): String =
+    String.join(items, ",")
+
+// Create a JSON error object: {"error": "message"}
+fn jsonErrorMsg(message: String): String =
+    jsonObject(jsonString("error", message))
+
+// Create a JSON message object: {"message": "text"}
+fn jsonMessage(text: String): String =
+    jsonObject(jsonString("message", text))
+
+// ============================================================
+// Usage Example (copy into your file)
+// ============================================================
+//
+// fn router(method: String, path: String, body: String): { status: Int, body: String } = {
+//     if method == "GET" && path == "/" then httpOk("Welcome!")
+//     else if method == "GET" && pathMatches(path, "/users/:id") then {
+//         match getPathSegment(path, 1) {
+//             Some(id) => httpOk(jsonObject(jsonString("id", id))),
+//             None => httpNotFound(jsonErrorMsg("User not found"))
+//         }
+//     }
+//     else httpNotFound(jsonErrorMsg("Not found"))
+// }
+//
+// fn main(): Unit with {Console, HttpServer} = {
+//     HttpServer.listen(8080)
+//     Console.print("Server running on port 8080")
+//     serveLoop(5)  // Handle 5 requests
+// }
+//
+// fn serveLoop(remaining: Int): Unit with {Console, HttpServer} = {
+//     if remaining <= 0 then HttpServer.stop()
+//     else {
+//         let req = HttpServer.accept()
+//         let resp = router(req.method, req.path, req.body)
+//         HttpServer.respond(resp.status, resp.body)
+//         serveLoop(remaining - 1)
+//     }
+// }

stdlib/lib.lux

@@ -3,6 +3,7 @@
 // This module re-exports the core standard library modules.
 // Import with: import stdlib
 
-// Re-export Html module
+// Re-export core modules
 pub import html
 pub import browser
+pub import http