Extends @liuhao1024's escape-normalized fix so the patch tool also
recovers when old_string carries a real tab byte and matches via the
`exact` strategy — which is the headline reproduction in the issue and
the most common case in practice (LLMs frequently get old_string right
because they re-read the file, but still serialize new_string's tabs as
two-character `\t`).
Instead of gating on the match strategy, decide per-sequence by looking
at the *matched region of the file*: only convert `\t` -> tab and
`\r` -> CR when the file region we're replacing actually contains the
corresponding control byte. That mirrors the region-based heuristic in
`_detect_escape_drift` and keeps legitimate writes of the literal
two-character string `"\t"` (e.g. patching `sep = "\t"` in Python
source) untouched — those files have a backslash+t in the matched
region, not a real tab, so new_string passes through verbatim. `\n` is
still excluded because newlines serialize correctly through JSON and
unescaping would corrupt source escape sequences far more often than
help.
E2E verified against the live `patch` tool: tab-indented file + literal
`\t` in new_string under both `exact` (Variant 1) and `escape_normalized`
(Variant 2) strategies now produces real tab bytes; a Python source line
containing `sep = "\t"` (legitimate literal backslash-t) survives a
patch unchanged.
Tests updated to cover both strategies and the legitimate-literal case,
and to assert that `\n` is intentionally preserved.
Refs #33733
78be458608