Phase 4: add structure, folding, and references

AGENTS.md

@@ -61,7 +61,8 @@ Last verified state (all green, `./jaigradle check` and `verifyPlugin` too):
 ```text
 dev.hgh.HarnessSmokeTest                    tests=2
 dev.hgh.jai.JaiFileTypeTest                 tests=4
-dev.hgh.jai.editor.JaiEditorSupportTest     tests=5
+dev.hgh.jai.editor.JaiEditorSupportTest     tests=7
+dev.hgh.jai.editor.JaiFoldingBuilderTest     tests=3
 dev.hgh.jai.highlighting.*                  tests=8
 dev.hgh.jai.lexer.JaiCorpusLexerTest        tests=2   <- the Tier 0 gate
 dev.hgh.jai.lexer.JaiLexerTest              tests=13
@@ -69,13 +70,15 @@ dev.hgh.jai.parser.JaiCorpusParserTest      tests=1   <- the Tier 3 gate
 dev.hgh.jai.parser.JaiParserGoldenTest      tests=5   <- Tier 2 golden trees
 dev.hgh.jai.parser.JaiParserLongTailTest    tests=1   <- focused parser regressions
 dev.hgh.jai.parser.DebugParseTest           tests=2   <- scratch harness, inert
--> total 43, failures+errors 0
+dev.hgh.jai.reference.JaiReferenceTest        tests=4
+dev.hgh.jai.structure.JaiStructureViewTest    tests=3
+-> total 55, failures+errors 0
 ```
 
 The corpus gates report what they actually did; check both lines are still there:
 
 ```text
-Tier 0: lexed 714 files, 17154195 chars, 3009381 tokens cleanly.
+Tier 0: lexed 714 files, 17154195 chars, 3008777 tokens cleanly.
 Tier 3: parsed 714 files, 714 clean (100.0%), 0 with errors, 0 PsiErrorElements total.
 ```
 
@@ -108,6 +111,10 @@ Tier 3: parsed 714 files, 714 clean (100.0%), 0 with errors, 0 PsiErrorElements
   `src/main/gen`, `JaiParserDefinition`, `JaiParserUtil`. Tier 2 golden trees and
   the Tier 3 corpus gate are green at **100.0% (714/714 files parse with zero
   `PsiErrorElement`)**.
+- **Phase 4** — structure view, folding for blocks/comments/here-strings, and
+  `#import`/`#load` path references with standard go-to-definition resolution.
+  Headless tests cover source-ordered declarations, nested structure members,
+  folding ranges, local `#load`, and Jai module directories.
 
 ### Lexer design facts worth knowing before touching it
 
@@ -162,16 +169,18 @@ Tier 3: parsed 714 files, 714 clean (100.0%), 0 with errors, 0 PsiErrorElements
 - **Directive flags require adjacency.** `#library,system` is a flag;
   `(cb: (*GUID) #c_call, ctx: *void)` is a parameter separator. Without the
   adjacency check the flag swallowed `, ctx`.
+- **Contributed references need a PSI host.** Generated AST wrappers do not
+  implement `ContributedReferenceHost`, so `literalExpr` uses the
+  `JaiReferenceHostMixin` from the BNF. Do not remove the mixin and expect a
+  `PsiReferenceContributor` to be queried through the standard reference service.
 
 ### Not done — pick up here
 
-1. **Phase 4** — structure view, folding, `#import`/`#load` reference resolution
-   and go-to-definition. The PSI is in place, and the Tier 3 corpus gate is now
-   fully green. `JaiFileTypeTest` used to document being blocked on the
-   `ParserDefinition`; that no longer applies.
-   `#asm` bodies are intentionally consumed opaquely, so nothing inside them has
-   PSI yet.
-2. **Phases 5+** — see the plan.
+1. **Phase 5** — completion (keywords, directives, module names), rename, and
+   find-usages; see `docs/BUILD_PLAN.md`.
+2. **Phases 6+** — formatter, inspections, compiler integration, and other
+   optional work remain. `#asm` bodies are intentionally consumed opaquely, so
+   nothing inside them has PSI yet.
 
 ### Open questions for the user (unanswered)