fix(plugins): close remaining gaps in new plugin format support

- Fix cmd_runtimes() help text: init.lua/init.rn → main.lua/main.rn
- Add .lua extension validation to owlry-lua manifest (mirrors Rune)
- Replace eprintln! with log::warn!/log::debug! in owlry-lua loader
- Add log = "0.4" dependency to owlry-lua
- Add tests: [[providers]] deserialization in owlry-core manifest,
  manifest provider fallback in owlry-lua and owlry-rune loaders,
  non-runtime plugin filtering in both runtimes

crates/owlry-lua/Cargo.toml

@@ -30,6 +30,9 @@ serde_json = "1.0"
 # Version compatibility
 semver = "1"
 
+# Logging
+log = "0.4"
+
 # HTTP client for plugins
 reqwest = { version = "0.13", default-features = false, features = ["native-tls", "blocking", "json"] }