initial: packwiz → simple-mod-sync manifest converter

Reads packwiz pack (pack.toml + index.toml + per-file .pw.toml) and
emits a simple-mod-sync sync_version=3 manifest. Drops server-only
mods, skips CurseForge metadata-mode entries with a warning, maps
content type from the parent directory of each metafile.

Optional --bundle-non-mods zips config/, options.txt etc into one
archive served as a 'packed' entry — covers the gap where simple-mod-sync
only ships zip-extractable content for non-mods.

15 tests, includes integration against upstream packwiz-example-pack.

tests/fixture-pack/index.toml

@@ -0,0 +1,39 @@
+hash-format = "sha256"
+
+[[files]]
+file = "mods/sodium.pw.toml"
+hash = "0000000000000000000000000000000000000000000000000000000000000000"
+metafile = true
+
+[[files]]
+file = "mods/fabric-api.pw.toml"
+hash = "0000000000000000000000000000000000000000000000000000000000000000"
+metafile = true
+
+[[files]]
+file = "mods/server-side-tool.pw.toml"
+hash = "0000000000000000000000000000000000000000000000000000000000000000"
+metafile = true
+
+[[files]]
+file = "mods/cf-only-mod.pw.toml"
+hash = "0000000000000000000000000000000000000000000000000000000000000000"
+metafile = true
+
+[[files]]
+file = "resourcepacks/branding.pw.toml"
+hash = "0000000000000000000000000000000000000000000000000000000000000000"
+metafile = true
+
+[[files]]
+file = "shaderpacks/iris.pw.toml"
+hash = "0000000000000000000000000000000000000000000000000000000000000000"
+metafile = true
+
+[[files]]
+file = "config/voicechat-client.properties"
+hash = "1111111111111111111111111111111111111111111111111111111111111111"
+
+[[files]]
+file = "options.txt"
+hash = "2222222222222222222222222222222222222222222222222222222222222222"