notes test: pause the game while the overlay is installed

[Alistair-Afton]

Summary

• overlay/notes tests depend on df.global.pause_state being true: NotesOverlay:onRenderFrame() skips drawing map pins when the game is unpaused in text mode.
• The test previously relied on the ambient pause state left by the test harness (ensure_fortress pauses once when entering fortress mode). Any earlier test that leaves the game unpaused breaks render_existing_notes (this happened in fix three plugin crash/UB bugs; test coverage for 14 plugins dfhack#5939 CI).
• install_notes_overlay now saves and sets pause_state; cleanup restores it, matching the existing waypoint/overlay-state save-restore pattern in this file.

Test plan

• test -t overlay/notes in-game: 5/5 tests, 17/17 checks pass

[SilasD]

requested change: use the existing API.

[Alistair-Afton]

Done in cfdefba - both sites now use dfhack.world.ReadPauseState()/SetPauseState(). Re-verified in-game: 5/5 notes tests pass.

Also applied the same API in the dfhack-side pause handling (test/plugins/autodump.lua, test/plugins/liquids.lua in dfhack#5939, commit 934c663f5) for consistency.

[SilasD]

I'm fine with this now.

for whatever reason, GitHub isn't letting me resolve those two conversations. maybe after I submit this comment.

Edit: GitHub was just being slow or wonky.

[SilasD]

What GitHub didn't do is show the approve button. maybe this time. Edit: nope. Maybe it's this pre-commit.ci workflow.