lib-lock: roll the save lock back to v0.45.0 (plus the Ubuntu 26.04 fix) for v0.45.2 #1131

Since v0.45.0, the save lock in scripts/lib-lock.sh has taken on takeover/recovery
features: #1106 (for #1101/#1103), then #1120, then #1123. Every review round since
has found a new two-simultaneous-holders interleaving: #1119, #1122, #1124/#1125,
PRs #1126 and #1129 (neither merged).

Decision: for v0.45.2, roll the lock back to exactly what v0.45.0 shipped, plus ONLY
the #1108 Ubuntu 26.04 fix (PR #1112, the noclobber-guarded pid write on the primary
mkdir path). Users ran the v0.45.0 lock for weeks without a two-holder report.
Redesign the takeover/recovery feature later, separately, with more review time.

This reopens #1101 and #1103 (the takeover/recovery feature they describe will no
longer ship in this form).

Maintainer-approved 2026-11-14.

[AI-generated]