docs(ffi-linkage): checkpoint — Phase 6.1 (sqlite) done; next Phase 6.2 (platform)

current/CHECKPOINT-EXTERN-EXPORT.md

@@ -5,7 +5,17 @@ Companion to `current/PLAN-EXTERN-EXPORT.md` — one merged plan: **Part A** add
 every commit, one step at a time per the cadence rule.
 
 ## Last completed step
-**Phase 5.1 — annotate A→B gate post-flip + add fn-rename case** (`test` commit
+**Phase 6.1 — migrate `vendors/sqlite` `#foreign`→`extern`** (`refactor` commit
+`410a52e`). **PART B PHASE 6 STARTED.** Pure source rename: all 97
+`sqlite3_* … #foreign sqlib "csym";` fn decls → `extern sqlib "csym";` (+ the one
+stale header-comment reference, line 9). The `extern_lib` axis references the `sqlib`
+`#import c` unit identically to `#foreign sqlib`, so IR/output is byte-identical —
+empty snapshot diff (only `sqlite.sx` changed), and example 1624
+(`vendor-sqlite-module`) stdout byte-unchanged. Suite green (647 corpus / 444 unit,
+0 failed). Remaining Phase 6 batches: 6.2 platform (~95), 6.3 std (~60), 6.4 ffi
+(~50), 6.5 remainder.
+
+### Prior: Phase 5.1 — annotate A→B gate post-flip + add fn-rename case (`test` commit
 `93e7b6f`). **PHASE 5 COMPLETE → PART B Phase 5 done.** The A→B gate
 (`lower.test.zig`) already asserted `#foreign` ≡ `extern`/`export` byte-identical IR
 for fn / global / Obj-C class; post-Phase-5.0 the fn-decl + data-global paths build
@@ -160,19 +170,23 @@ AOT), 1227 (export fn rename, AOT), 1348 (objc extern class), 1349 (objc export
 (jni extern class), 1174/1175 (interplay diagnostics).
 
 ## Next step
-**PART B — Phase 6 (migrate stdlib `#foreign`→`extern`, empty snapshot diff per
-batch).** Phase 5 (parser routing 5.0 + gate lock 5.1) is COMPLETE.
+**PART B — Phase 6.2 (migrate `library/modules/platform/` `#foreign`→`extern`,
+~95 sites).** Phase 6.1 (sqlite) is COMPLETE.
 
-- **Phase 6** (`refactor` batches, one commit per batch, snapshot diff must be EMPTY):
-  rewrite `library/` `#foreign`→`extern` (fns/globals), `#foreign #objc_class`→
-  `#objc_class … extern`, defined classes → `… export`. Pure SOURCE rename — the AST is
-  already unified, so IR/output must be byte-identical per batch. A non-empty diff ⇒ a
-  reader still branches on `foreign_expr` structurally → STOP and coalesce it first
-  (don't regen). Batches (from PLAN-EXTERN-EXPORT Phase 6): 6.1 `library/vendors/sqlite/`
-  (~98 sites), 6.2 `library/modules/platform/` (uikit/android/android_jni/sdl3, ~95),
-  6.3 `library/modules/std/` (socket/thread/fs/time/process, ~60), 6.4
-  `library/modules/ffi/` (objc/raylib/objc_block, ~50), 6.5 remaining `library/`+
-  `vendors/`. Then **Phase 7** migrates examples + issues the same way.
+- **Phase 6.2** (`refactor`, snapshot diff must be EMPTY): rewrite
+  `library/modules/platform/` (uikit/android/android_jni/sdl3) `#foreign`→`extern`
+  (fns/globals), `#foreign #objc_class`→`#objc_class … extern`, defined classes →
+  `… export`. ⚠ Unlike sqlite (uniform fn decls), platform mixes Obj-C/JNI runtime
+  CLASSES — those use the **postfix** form (`#objc_class("X") extern { … }` for a
+  reference/import class == `#foreign #objc_class`; `… export` for a defined class ==
+  bare `#objc_class`). Check each `#foreign` site's shape before bulk-replacing; a
+  naive `s/#foreign //` is WRONG for the class-prefix form. Pure SOURCE rename, IR
+  byte-identical; a non-empty diff ⇒ a reader still branches on `foreign_expr`
+  structurally → STOP and coalesce first (don't regen).
+- **Remaining Phase 6 batches:** 6.3 `library/modules/std/`
+  (socket/thread/fs/time/process, ~60), 6.4 `library/modules/ffi/`
+  (objc/raylib/objc_block, ~50), 6.5 remaining `library/`+`vendors/`. Then **Phase 7**
+  migrates examples + issues the same way.
 - **Phases 6–7** (`refactor` batches, empty snapshot diff per batch): migrate the
   stdlib + examples from `#foreign` spelling to `extern`. Because the AST is already
   unified, this is a pure SOURCE rename (`… #foreign LIB "sym";` → `… extern LIB "sym";`
@@ -295,6 +309,11 @@ Part A ratified (bare / postfix / `⇒ callconv(.c)` / lib-separate). Part B:
   deleted at cutover). Affects only diagnostic wording — IR/behavior identical either way.
 
 ## Log
+- (6.1 sqlite) **PHASE 6 STARTED.** Migrated `vendors/sqlite/sqlite.sx`: 97
+  `… #foreign sqlib "csym";` fn decls → `extern sqlib "csym";` (+ line-9 comment).
+  `extern_lib` references the `sqlib` `#import c` unit like `#foreign sqlib`; IR
+  byte-identical, empty snapshot diff, example 1624 stdout unchanged. Suite green
+  (647/444). `refactor` `410a52e`.
 - (5.1 gate annotate) **PHASE 5 COMPLETE.** Annotated the A→B gate header
   (`lower.test.zig`) to record that post-Phase-5.0 the fn/global `#foreign` paths
   build the same extern-named AST → cases 1/2 are structurally (not coincidentally)