Implement Jai formatter

AGENTS.md

@@ -61,7 +61,7 @@ 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.completion.JaiCompletionTest      tests=19
+dev.hgh.jai.completion.JaiCompletionTest      tests=20
 dev.hgh.jai.editor.JaiEditorSupportTest       tests=7
 dev.hgh.jai.editor.JaiFoldingBuilderTest      tests=3
 dev.hgh.jai.findusages.JaiFindUsagesTest      tests=2
@@ -73,11 +73,12 @@ 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
 dev.hgh.jai.refactoring.JaiRenameTest          tests=3
-dev.hgh.jai.reference.JaiReferenceTest         tests=9
+dev.hgh.jai.reference.JaiReferenceTest         tests=10
 dev.hgh.jai.structure.JaiStructureViewTest     tests=3
+dev.hgh.jai.formatter.JaiFormatterTest          tests=4
 dev.hgh.jai.settings.JaiProjectSettingsTest    tests=3
 dev.hgh.jai.settings.JaiConfiguredRootTest    tests=6
--> total 93, failures+errors 0
+-> total 99, failures+errors 0
 ```
 
 The corpus gates report what they actually did; check both lines are still there:
@@ -129,6 +130,10 @@ Tier 3: parsed 714 files, 714 clean (100.0%), 0 with errors, 0 PsiErrorElements
   sources. Headless tests cover state round-tripping, the Settings panel,
   custom-root `#import`/`#load` navigation and completion, and cross-root
   find-usages.
+- **Phase 6** — PSI-aware formatter with operator/punctuation spacing,
+  block indentation, opaque `#asm` preservation, and a corpus-wide idempotence
+  gate. Headless formatter tests cover registration, representative formatting,
+  opaque/directive token preservation, and all 714 corpus files.
 
 ### Lexer design facts worth knowing before touching it
 
@@ -197,16 +202,14 @@ Tier 3: parsed 714 files, 714 clean (100.0%), 0 with errors, 0 PsiErrorElements
 
 ### In progress — pick up here
 
-1. **Phases 6+** — formatter, inspections, compiler integration, and other
-   optional work remain. `#asm` bodies are intentionally consumed opaquely, so
-   nothing inside them has PSI yet.
+1. **Phases 7+** — inspections, compiler integration, and other optional work
+   remain. `#asm` bodies are intentionally consumed opaquely, so nothing inside
+   them has PSI yet.
 
 ### Next planned increment
 
-- Decide whether to continue with the optional formatter, inspections, and
-  compiler integration phases (6–8).
-- If formatter work begins, add the corpus-wide idempotence gate described in
-  `docs/BUILD_PLAN.md` before changing formatting behavior.
+- Decide whether to continue with inspections and compiler integration phases
+  (7–8).
 
 ### Open questions for the user (unanswered)