docs(common): correct ST sequence metadata and comment typos

- EscapeSequenceParser: ESC ST is ESC backslash (0x1B 0x5C), not ESC
  plus a double-quote character; align @vt metadata with C1 ST on the
  following line.
- Color.contrastRatio: document l2 as the second luminance argument.
- Marker.dispose: fix "change" -> "chance" in dispose listener comment.
- Buffer.clear: fix possessive "it's" -> "its" in JSDoc.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/common/Color.ts

@@ -373,7 +373,7 @@ export function toPaddedHex(c: number): string {
 /**
  * Gets the contrast ratio between two relative luminance values.
  * @param l1 The first relative luminance.
- * @param l2 The first relative luminance.
+ * @param l2 The second relative luminance.
  * @see https://www.w3.org/TR/WCAG20/#contrast-ratiodef
  */
 export function contrastRatio(l1: number, l2: number): number {