fix(bun): add tag_prefix to strip bun- from version tags

Bun releases use tags like bun-v1.2.3. Without tag_prefix, the version
included the bun- prefix, causing mismatches. Also update comparecache
with bun version normalizer for accurate comparison.

bun/releases.conf

@@ -1,6 +1,7 @@
 source = github
 owner = oven-sh
 repo = bun
+tag_prefix = bun-
 # non-baseline=amd64v3, -baseline=amd64
 default_x86_64 = x86_64_v3
 x86_64_v2 = baseline

cmd/comparecache/main.go

@@ -556,6 +556,11 @@ func normalizeVersionFunc(pkg string) func(string) string {
 			}
 			return v
 		}
+	case "bun":
+		return func(v string) string {
+			// bun: bun-v1.3.9 → v1.3.9
+			return strings.TrimPrefix(v, "bun-")
+		}
 	case "watchexec":
 		return func(v string) string {
 			// watchexec monorepo: cli-v1.20.5 → v1.20.5