read: paginated binary detection misfires on single control-char-dense lines (ANSI logs)

Describe the bug

packages/core/src/tool/read-filesystem.ts detects binary files differently depending on the read path:

• Whole-file read checks the first 64 KB as one buffer (binary(resource, first)).
• Paginated read (offset/limit, or large files) calls binary(resource, segment) per line, with the same nonPrintable / bytes.length > 0.3 threshold.

A single line dense in control characters (ANSI escape sequences in colored logs, backspace progress bars) can exceed 30% on that one line and fail the entire read with BinaryFileError — while reading the same file without offset succeeds. So page 2 of a log can suddenly report "binary".

Suggested fix

Apply the non-printable heuristic over a larger window in the paginated path too, rather than per single line.

Environment

• opencode version: latest dev