feat: column-aware CSV loading and changelog

- Replaced manual CSV parsing with csv crate, columns now looked up by name
- Fixed Rust example path and contract_size
- Added CHANGELOG.md for release tracking

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/data.rs

@@ -1,31 +1,28 @@
-use std::fs::File;
-use std::io::{BufRead, BufReader};
 use crate::types::Bar;
 use chrono::DateTime;
+use csv::Reader;
+use std::fs::File;
 
 pub fn load_csv(path: &str) -> Vec<Bar> {
     let file = File::open(path).expect("Could not open file");
-    let reader = BufReader::new(file);
+    let mut rdr = Reader::from_reader(file);
+    let headers = rdr.headers().expect("could not read headers").clone();
+    let col = |name: &str| headers.iter().position(|h| h == name).expect(name);
     let mut bars = Vec::new();
 
-    for line in reader.lines().skip(1) { //skips the header row
-        let line = line.expect("could not read line");
-        let cols: Vec<&str> = line.split(',').collect();
+    for result in rdr.records() {
+        let r = result.expect("could not read record");
+        let dt = DateTime::parse_from_rfc3339(&r[0]).expect("Bad timestamp");
 
-        let dt = DateTime::parse_from_rfc3339(cols[0]).expect("Bad Timestamp"); // this handles the timestamp to be in 2024-01-01 00:00:00 kind of way 
-
-        let bar = Bar {
+        bars.push(Bar {
             timestamp: dt.timestamp(),
-            open:      cols[1].parse().expect("Bad open"),
-            high:      cols[2].parse().expect("Bad high"),
-            low:       cols[3].parse().expect("Bad low"),
-            close:     cols[4].parse().expect("Bad close"),
-            volume:    cols[5].parse().expect("Bad volume"),
-        };
-
-        bars.push(bar); // pushes each bar from the csv to an element in Bar 
-
+            open: r[col("open")].parse().expect("Bad open"),
+            high: r[col("high")].parse().expect("Bad high"),
+            low: r[col("low")].parse().expect("Bad low"),
+            close: r[col("close")].parse().expect("Bad close"),
+            volume: r[col("volume")].parse().expect("Bad volume"),
+        });
     }
 
     bars
-}
+}