[bfrancojr]

Fixes #145.

check_decode printed a PXF rejection without its position. protowire-go prints reject: L:C: msg. The library already keeps the position on the Status, so PxfDecode and PxfPb now print Status::ToString(), which gives line:col: msg. The PB and SBE paths carry no position and are unchanged.

Evidence (macOS, on main a632c6e):

• New ctests check_decode_position_pxf and check_decode_position_pxf-pb run the binary on testdata/check_decode/unknown-field.pxf and expect reject: 3:3: unknown field "nope" in test.v1.AllTypes. That is the text protowire-go's check_decode prints for the same input, measured on check_decode: a PXF rejection leaves out the line:col prefix that protowire-go prints #145.
• With main's main.cc restored, both tests fail (Required regular expression not found). With the fix, both pass.
• Full ctest: 100% passed, 658 of 658.
• clang-format 18: clean.

No gate verdict changes. The spec's cross_security_check.sh sends check_decode's output to /dev/null and judges by exit code alone, which this PR leaves unchanged (read in the script at spec main 0317811).

[bfrancojr]

Rebased onto main e1c1b72 (#136 merged); head is now 4b516a6. The PR's own diff is unchanged, checked by comparing its added and removed lines before and after the rebase. Local ctest at this head: 665 of 665.

[bfrancojr]

Rebased onto main df6b102; head is now cd52edd. The diff is unchanged. Local ctest: 691 of 691.

[bfrancojr]

Rebased onto main 9b9860a: cd52edd → 1695e1d. The earlier red "Differential against protowire-go" was Stream codecs differ: (run log). This branch was based on df6b102, from before #137 fixed the SBE stream difference. The rebase picks up #137, so the differential should now pass. The diff is unchanged. Locally: build OK, ctest 100% tests passed out of 707. The remote head was read back with git ls-remote: 1695e1d.

[bfrancojr]

Rebased onto main 96edbdd, after #139 merged, to clear a CHANGELOG.md conflict: 1695e1d → 59fc070. The code is unchanged, and the CHANGELOG still gets one added line. Locally: build OK, ctest 100% tests passed out of 710. Every check had passed on 1695e1d. The remote head was read back with git ls-remote: 59fc070.