rewrite-go: ship parity with JS / Python / C# ports (#7557)

Full RPC handler surface, recipe-author primitives, type attribution,
test harness, and recipe library brought to parity with the JavaScript,
Python, and C# language ports.

RPC handler surface
- Parse / ParseProject (project-aware: module + goModContent; per-file
  closest-ancestor go.mod ownership; sibling go.sum populates
  ResolvedDependencies).
- BatchVisit returns {modified, deleted, hasNewMessages, searchResultIds};
  searchResultIds walker registered, hasNewMessages snapshot tracked.
- Generate drives ScanningRecipe.Generate.
- GetMarketplace emits full descriptor (recipeList, dataTables,
  preconditions, maintainers, contributors, examples, option types).
- PrepareRecipe returns per-instance UUID.
- TraceGetObject for RPC tracing.
- Server CLI flags: --log-file, --trace-rpc-messages, --metrics-csv,
  --recipe-install-dir, --data-tables-csv-dir.

Recipe-author surface
- recipe.Recipe + recipe.Base, ScanningRecipe end-to-end.
- recipe.DataTable[Row] generic + InMemoryDataTableStore +
  CsvDataTableStore.
- visitor.GoVisitor.Cursor() / SetCursor() for RPC seeding;
  visitor.BuildChain reconstructs cursors from RPC IDs.
- Cursor message map: PutMessage, GetNearestMessage,
  PollNearestMessage, etc.
- recipe.Service[T](sourceFile) registry + GoVisitor.DoAfterVisit
  composition.
- Five services: ImportService, AutoFormatService, AnnotationService,
  WhitespaceValidationService, NamingService.
- Five foundational recipes: AddImport, RemoveImport,
  RemoveUnusedImports, OrderImports, RenamePackage.

Type attribution
- Same-package multi-file resolution via parser.ParsePackage.
- Third-party module resolution via go.mod requires + vendor walker
  (parses <projectRoot>/vendor/<modulePath>/*.go for real
  JavaTypeMethod attribution; honors `replace` directives).
- tree.GoResolutionResult marker (Module, Requires, Replaces,
  Excludes, Retracts, ResolvedDependencies); both Go-side and
  Java-side RPC codecs.
- parser.ProjectImporter 3-tier lazy resolver
  (sources -> requires -> stdlib).
- Build-tag file inclusion: parser.MatchBuildContext recognizes
  //go:build, // +build, and filename suffixes; default
  build.Default with recipe-author override.
- Cross-package generics across the corpus.

RPC sender / receiver visitor-pattern refactor
- Senders / receivers on both sides extend the language visitor
  (visitor.GoVisitor on Go, JavaVisitor<RpcSendQueue/ReceiveQueue>
  on Java) and override VisitX, mirroring rewrite-java.
- Eliminated ~600 LOC of switch boilerplate.
- tree.J got polymorphic GetID / GetPrefix / GetMarkers; mutators
  intentionally NOT on the interface (would break RecipeScheduler
  identity-based change detection).

Annotations
- tree.Annotation (J-shaped) + LeadingAnnotations on
  VariableDeclarations, MethodDeclaration, TypeDecl on both Go and
  Java sides.
- Struct field tags AND //go:/lint: directives uniformly modeled as
  J.Annotation; printer reassembles backticks for tags and //<name>
  lines for directives.
- AnnotationService surface mirrors rewrite-java
  (AllAnnotations, IsAnnotatedWith, FindAnnotations,
  AddAnnotationVisitor, RemoveAnnotationVisitor).

Test harness
- Java: Assertions.go(...), goMod(...), goProject(name, ...) sibling
  pattern matching mavenProject(...).
- Go: test.RewriteRun + test.Golang(...), test.GoMod(...),
  test.GoSum(...), test.GoProject(name, ...).
- propagateModuleResolution copies the parsed go.mod marker onto
  every sibling .go CU at project expansion so cross-file recipes
  read module context per file.
- ExpectType / ExpectPrimitiveType / ExpectMethodType helpers on
  both sides.
- GoMod conformance corpus (10 cases) shared across Go + Java tests.
- Printer parity corpus (13 fixtures across gofmt/ + generics/),
  opt-in via `make parity`, never in CI.

Recipe-author guide at doc/recipe-authoring.md.
PLAN.md removed: contents are now reflected in the codebase, doc, and
shipped tests.

Author: jkschneider

rewrite-go/.gitignore

@@ -1 +1 @@
-rewrite/test-classpath.txt
+test-classpath.txt

rewrite-go/Makefile

@@ -0,0 +1,16 @@
+.PHONY: test parity
+
+# Default test run — what CI executes. Build-tag-gated tests stay out.
+test:
+	go test ./...
+
+# Printer fidelity audit. Loads every fixture under
+# test/printer-corpus/, parses + prints, and asserts byte-equality.
+# Gated behind the `parityaudit` build tag so it never runs in CI;
+# devs invoke it manually when investigating printer regressions.
+#
+# Trade-off (per the eng review's P2 decision): corpus regressions ship
+# undetected by automation in exchange for fast iteration and simple
+# test infra. Re-evaluate if a corpus-detectable bug ever lands.
+parity:
+	go test -tags parityaudit ./pkg/printer/...

rewrite-go/PLAN.md

@@ -30,6 +30,12 @@ tasks.withType<Javadoc>().configureEach {
     exclude("**/G.java")
 }
 
+// Test fixtures for the GoMod conformance corpus are .gomod / .gosum / .json
+// files; none of these formats accept a leading license header.
+configure<nl.javadude.gradle.plugins.license.LicenseExtension> {
+    excludePatterns.addAll(listOf("**/*.gomod", "**/*.gosum", "**/*.json"))
+}
+
 val goBuild = tasks.register<Exec>("goBuild") {
     workingDir = projectDir
     // Use relative path to avoid absolute paths in cache key (Exec args are cache inputs)