chore(routing): flip swift-url-routing pin to branch main (W3) + mechanical drift fixes

- Package.swift: swift-url-routing 0.6.0 -> branch:"main"; removed stale
  "do NOT use branch:main" fork-pin comments (now false, this wave lands
  the rewrite).
- Deleted Sources/URLFormCodingURLRouting/Form.Conversion.swift: the W2
  rewrite folded an identical Form.Conversion<Value> into URLRouting
  itself (URLRouting now depends on URLFormCoding directly), so the local
  copy caused an "ambiguous type name" collision. Dissolved in favor of
  the vended equivalent (same name/signature, upgraded to typed throws).
- URLRouting.Conversion.swift: Conversions.Map -> Parser.Conversion.Map
  (W2 rename of the conversion-chaining combinator).

Build/test green (167 tests passed).

Author: coenttb

Package.swift

@@ -14,8 +14,6 @@ extension Target.Dependency {
     static var urlFormCodingURLRouting: Self { .target(name: .urlFormCodingURLRouting) }
     static var rfc2388: Self { .product(name: "RFC 2388", package: "swift-rfc-2388") }
     static var whatwgUrlEncoding: Self { .product(name: "WHATWG Form URL Encoded", package: "swift-whatwg-url") }
-    // Institute fork URL (principal ruling 2026-07-09); pinned to upstream-identical tags
-    // (0.6.2 = pointfree release SHA); do NOT use branch:main until the RFC-first rewrite lands via the routing arc.
     static var urlRouting: Self { .product(name: "URLRouting", package: "swift-url-routing") }
 }
 
@@ -40,10 +38,8 @@ let package = Package(
     dependencies: [
         .package(url: "https://github.com/swift-ietf/swift-rfc-2388.git", branch: "main"),
         .package(url: "https://github.com/swift-whatwg/swift-whatwg-url.git", branch: "main"),
-        // Institute fork URL (principal ruling 2026-07-09); pinned to upstream-identical tags
-        // (0.6.2 = pointfree release SHA); do NOT use branch:main until the RFC-first rewrite lands via the routing arc.
         // This backs the standalone URLFormCodingURLRouting product only; the URLFormCoding product is unaffected.
-        .package(url: "https://github.com/swift-foundations/swift-url-routing.git", from: "0.6.0")
+        .package(url: "https://github.com/swift-foundations/swift-url-routing.git", branch: "main")
     ],
     targets: [
         .target(

Sources/URLFormCodingURLRouting/Form.Conversion.swift

@@ -89,7 +89,7 @@ extension URLRouting.Conversion {
         _ type: Value.Type,
         decoder: Form.Decoder = .init(),
         encoder: Form.Encoder = .init()
-    ) -> Conversions.Map<Self, Form.Conversion<Value>> {
+    ) -> Parser.Conversion.Map<Self, Form.Conversion<Value>> {
         self.map(.form(type, decoder: decoder, encoder: encoder))
     }
 }