fix: match the narrowest distinctive fragment, and stop padding STALE

Integrating into Bari 206 turned up a pattern that cannot match correctly
formatted source. Its CLAP_DESCRIPTION is long enough that rustfmt wraps
the assignment:

    const CLAP_DESCRIPTION: Option<&'static str> =
        Some("Multiband compressor/limiter (...)");

A site pattern spanning `const ... = Some("...")` never matches that, and
the fix is general rather than specific to this field: a site pattern
should be the narrowest fragment that is still distinctive, so formatting
decisions above it cannot break the check. Some("...") is unique enough
and lives on one line whatever rustfmt does with the rest.

Also stops appending a bare newline to STALE when nothing was retired,
which a no-op regeneration does on every run.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WHt4DykxXaQnyaJfyS8KCn

tools/branding-sites.tsv

@@ -28,7 +28,7 @@ req	authors.cargo	Cargo.toml	authors = ["Your Name <your@email.com>"]
 req	homepage.cargo	Cargo.toml	homepage = "https://github.com/YOUR-USERNAME/YOUR-PLUGIN-NAME"
 req	url.plugin	src/lib.rs	const URL: &'static str = env!("CARGO_PKG_HOMEPAGE")
 req	description.cargo	Cargo.toml	description = "A minimal NIH-plug audio plugin"
-req	description.clap	src/lib.rs	const CLAP_DESCRIPTION: Option<&'static str> = Some("Your plugin description")
+req	description.clap	src/lib.rs	Some("Your plugin description")
 req	clapid.plugin	src/lib.rs	const CLAP_ID: &'static str = "com.your-domain.plugin-name"
 req	vst3id.plugin	src/lib.rs	const VST3_CLASS_ID: [u8; 16] = *b"Unique16CharId!!"
 req	struct.def	src/lib.rs	struct MyPlugin {