Add explicit size checks before casting long values to int in two locations in the buildpack module where external data (file sizes, Docker stream headers) could exceed Integer.MAX_VALUE.

Content.of(File): file.length() returns long but was cast to int without validation. Files larger than 2GB would silently produce incorrect (possibly negative) size values, corrupting tar entry headers. Now throws IllegalStateException with the actual file size in the message.

LogUpdateEvent.read(): The size parameter is parsed from a Docker multiplexed stream header (4 unsigned bytes, max ~4GB). Values exceeding Integer.MAX_VALUE would cause NegativeArraySizeException when allocating the byte array. Now throws IllegalStateException with the actual byte count. The error is caught by readAll() and forwarded as a STD_ERR log event, matching the existing error handling pattern.

Both assertions use the lambda-with-formatted-value pattern already established by StreamType.forId() in the same file. Tests added for both overflow paths.