v0.19.2 — file-edit data integrity

An eleventh adversarial review, of the file-mutation surface (edit_file / apply_patch / write_file). The logic guards (unique-anchor, path-jail, write-region) reviewed clean — the exposure was entirely at the byte-I/O layer, and it's the kind of silent corruption this surface exists to prevent.

Fixed

• File edits no longer silently rewrite every line ending. Reads/writes went through Path.read_text/write_text, whose universal-newline translation flipped the WHOLE file to the platform's line ending — a one-line edit on an LF file became a whole-file CRLF diff on Windows (and an LF-flatten on Linux). Edits now read as bytes normalized to \n for matching and write back preserving the file's original newline convention. (A CRLF file also now anchors a model's \n-based match string correctly.)
• File writes are crash-atomic — temp file + os.replace, so a crash or I/O error mid-write can't truncate the user's existing file.
• apply_patch anchors every hunk against the ORIGINAL content (not a copy mutated by earlier hunks) and rejects overlapping target regions.
• Non-UTF-8 files get a clear "not a UTF-8 text file" error instead of an opaque failure — and are never touched.

Note: the newline bug predates the 0.19.x line (it's been in the file tools since surgical editing landed) — this is the fix, not a fresh regression.

Gate: 1447 passed / 3 skipped, mypy + ruff green (+8 byte-level tests).

Upgrade (recommended for anyone using edit_file/apply_patch): `pip install --upgrade 'chimera-agent[full]'`