chore: move bundle into Ace3/ subfolder + standard .gitignore

Matches the Exiles fork-layout convention (one folder per addon). README
and tools/sweep.py updated for the new path; tools/sweep.py stays at repo
root since it's dev tooling, not part of the shipped bundle.

README.md

@@ -57,11 +57,14 @@ Or replace the entire `Libs/Ace3/` tree in one go.
 
 ### Option 2: standalone addon
 
-Drop the contents (except `README.md` / `.gitattributes`) into
-`Interface/AddOns/Ace3/` and the loadable `Ace3.toc` will register every library at top
+Drop the **`Ace3/`** directory from this repo straight into
+`Interface/AddOns/` and the loadable `Ace3.toc` will register every library at top
 priority via LibStub. Useful for non-bundling forks (`chatter`, `sexymap`, `clique`, …) to
 get Ace without each one carrying its own copy.
 
+(The canonical bundle lives under `Ace3/` at the repo root so this repo follows the same
+"each addon in its own folder" layout as every other `Exiles/coa-*` fork.)
+
 ## Sync policy
 
 Bumping upstream means a single commit here, then a sweep across every fork that embeds these