lib-vt: move scrollback limits to terminal_set

Terminal construction previously accepted GhosttyTerminalOptions with
dimensions and one scrollback byte limit. Remove the options struct from
the ABI and make ghostty_terminal_new accept columns and rows directly.

Add byte and line limit options to ghostty_terminal_set and forward them
to the runtime Terminal setters. NULL removes a limit, while zero bytes
disables scrollback. Update type metadata, tests, and all API examples.

include/ghostty/vt/key.h

@@ -42,8 +42,7 @@
  * @code{.c}
  * // Create a terminal and feed it some VT data that changes modes
  * GhosttyTerminal terminal;
- * ghostty_terminal_new(NULL, &terminal,
- *     (GhosttyTerminalOptions){.cols = 80, .rows = 24, .max_scrollback = 0});
+ * ghostty_terminal_new(NULL, &terminal, 80, 24);
  *
  * // Application might write data that enables Kitty keyboard protocol, etc.
  * ghostty_terminal_vt_write(terminal, vt_data, vt_len);

include/ghostty/vt/mouse.h

@@ -39,8 +39,7 @@
  * @code{.c}
  * // Create a terminal and feed it some VT data that enables mouse tracking
  * GhosttyTerminal terminal;
- * ghostty_terminal_new(NULL, &terminal,
- *     (GhosttyTerminalOptions){.cols = 80, .rows = 24, .max_scrollback = 0});
+ * ghostty_terminal_new(NULL, &terminal, 80, 24);
  *
  * // Application might write data that enables mouse reporting, etc.
  * ghostty_terminal_vt_write(terminal, vt_data, vt_len);

include/ghostty/vt/terminal.h

@@ -172,26 +172,6 @@ extern "C" {
  * @{
  */
 
-/**
- * Terminal initialization options.
- *
- * @ingroup terminal
- */
-typedef struct {
-  /** Terminal width in cells. Must be greater than zero. */
-  uint16_t cols;
-
-  /** Terminal height in cells. Must be greater than zero. */
-  uint16_t rows;
-
-  /** Maximum number of lines to keep in scrollback history. */
-  size_t max_scrollback;
-
-  // TODO: Consider ABI compatibility implications of this struct.
-  // We may want to artificially pad it significantly to support
-  // future options.
-} GhosttyTerminalOptions;
-
 /**
  * Amount of compression work to perform before returning.
  *
@@ -888,6 +868,28 @@ typedef enum GHOSTTY_ENUM_TYPED {
    * Input type: GhosttyTerminalClipboardWriteFn
    */
   GHOSTTY_TERMINAL_OPT_CLIPBOARD_WRITE = 26,
+
+  /**
+   * Set the maximum scrollback allocation in bytes.
+   *
+   * Lowering the limit immediately removes eligible complete historical
+   * pages. A value of zero disables scrollback and erases retained history.
+   * A NULL value pointer removes the byte limit.
+   *
+   * Input type: size_t*
+   */
+  GHOSTTY_TERMINAL_OPT_SCROLLBACK_MAX_BYTES = 27,
+
+  /**
+   * Set the maximum number of physical lines retained in scrollback.
+   *
+   * Lowering the limit immediately removes eligible complete historical
+   * pages. The effective limit retains the active-area and page-granularity
+   * minimums. A NULL value pointer removes the line limit.
+   *
+   * Input type: size_t*
+   */
+  GHOSTTY_TERMINAL_OPT_SCROLLBACK_MAX_LINES = 28,
   GHOSTTY_TERMINAL_OPT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyTerminalOption;
 
@@ -1221,16 +1223,22 @@ typedef enum GHOSTTY_ENUM_TYPED {
 /**
  * Create a new terminal instance.
  *
+ * The terminal starts with various reasonable defaults e.g. around
+ * scrollback limits. Use ghostty_terminal_set() to change any options
+ * prior to using the terminal.
+ *
  * @param allocator Pointer to allocator, or NULL to use the default allocator
  * @param terminal Pointer to store the created terminal handle
- * @param options Terminal initialization options
+ * @param cols Terminal width in cells (must be greater than zero)
+ * @param rows Terminal height in cells (must be greater than zero)
  * @return GHOSTTY_SUCCESS on success, or an error code on failure
  *
  * @ingroup terminal
  */
 GHOSTTY_API GhosttyResult ghostty_terminal_new(const GhosttyAllocator* allocator,
-                                   GhosttyTerminal* terminal,
-                                   GhosttyTerminalOptions options);
+                                               GhosttyTerminal* terminal,
+                                               uint16_t cols,
+                                               uint16_t rows);
 
 /**
  * Free a terminal instance.
@@ -1291,7 +1299,8 @@ GHOSTTY_API GhosttyResult ghostty_terminal_resize(GhosttyTerminal terminal,
  * write_pty callback and userdata pointer. The value is passed
  * directly for pointer types (callbacks, userdata) or as a pointer
  * to the value for non-pointer types (e.g. GhosttyString*).
- * NULL clears the option to its default.
+ * The behavior of a NULL value is specific to each option and is
+ * documented by the corresponding GhosttyTerminalOption value.
  *
  * Callbacks are invoked synchronously during ghostty_terminal_vt_write().
  * Callbacks must not call ghostty_terminal_vt_write() on the same