fix(scripts): add explicit utf-8 encodings

[LeonSGP43]

Summary

• add explicit encoding="utf-8" to text reads/writes in scripts/lint_diff.py
• add explicit encoding="utf-8" to the compare path in scripts/profile-tui.py
• add explicit encoding="utf-8" to duration cache reads/writes in scripts/run_tests_parallel.py

Verification

• ruff check --select PLW1514 scripts/lint_diff.py scripts/profile-tui.py scripts/run_tests_parallel.py
• python -m py_compile scripts/lint_diff.py scripts/profile-tui.py scripts/run_tests_parallel.py
• git diff --check

Fixes #36649

[alt-glitch]

Appears to be a duplicate of #36828, which makes the same utf-8 encoding fix to the same script files (lint_diff.py, profile-tui.py, run_tests_parallel.py) for the same issue #36649. Flagging for dedup.

[teknium1]

Thanks for the focused cross-platform fix. Current main still contains the five bare text-I/O sites this PR changes: scripts/lint_diff.py:33,200, scripts/profile-tui.py:519, and scripts/run_tests_parallel.py:482,504. The proposed encoding="utf-8" arguments directly satisfy the active PLW1514 policy in pyproject.toml:375-386.

GitHub currently reports the branch as conflict-dirty, but the current target statements remain present, so salvaging this is a mechanical reapplication of the same five substitutions onto HEAD.

Automated hermes-sweeper review.

[teknium1]

Closing — the sites this PR touched are already explicit-encoding on current main (PLW1514 ruff gate, enabled and enforced in lint CI). The class can't regress. Thanks for the sweep work.