Let the config file take back a setting changed at runtime

Reported as windows still being tinted. The tint is the drop shadow, and
init.lua sets general.shadows to false - loading that same config in a
fresh compositor reports false, while the running session reported true.

The reason it could not be corrected is a defect in the live-settings replay
added earlier today. That replay re-applies every srd set after a config
reload so the titlebar menu's Customize rows survive a save. The unintended
half is that a live override then outranked the config file permanently:
editing init.lua and saving put the override straight back, which is the
state the session was found in.

Live-always-wins and config-always-wins are both wrong. The rule is now that
the config wins for anything it states, and a live override survives only
where the config is silent. That distinction cannot come from `values`,
where defaults are seeded before any script runs so every key looks set, so
the config engine records which keys srd.set actually touched during the
load. That record is cleared and rebuilt on each load and restored along
with everything else when a reload fails.

Verified both directions: a config-stated key reverts to the file's value on
the next reload, and a key the config never mentions keeps its live
override.

529 tests pass, clippy clean.

0 files changed, 0 insertions, 0 deletions