docs(ffi-linkage): checkpoint — Phase 6.3 (std) done; next Phase 6.4 (ffi)

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 6.2 — migrate `platform/` `#foreign`→`extern`/`export`** (`refactor` commit
+**Phase 6.3 — migrate `std/` `#foreign`→`extern`** (`refactor` commit `59f90d2`).
+Pure source rename across 11 std modules (~60 sites):
+cli/core/fmt/fs/log/net.kqueue/process/socket/thread/time/trace. All fn-decl markers
+— bare `#foreign;`, `#foreign libc;`/`#foreign tlib;` (LIB ref), and
+`#foreign libc "csym";` (LIB+rename) → the same `extern …` tail (`extern` carries the
+identical `[LIB] ["csym"]` axis); plus 2 stale comment mentions (fmt/fs). No class
+forms in std. These modules ARE host-corpus-exercised → empty snapshot diff is direct
+validation. Suite green (647 corpus / 444 unit, 0 failed). Remaining Phase 6 batches:
+6.4 ffi (~50, has runtime classes), 6.5 remainder.
+
+### Prior: Phase 6.2 — migrate `platform/` `#foreign`→`extern`/`export` (`refactor` commit
 `2cd5d7b`). Pure source rename across uikit/android/android_jni/sdl3 (~64 sites):
 30 fn `… #foreign;`→`… extern;`; 34 import runtime classes
 `#foreign #objc_class/#jni_class("X") {`→`#…_class("X") extern {` (prefix→postfix);
@@ -184,19 +194,19 @@ 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 6.3 (migrate `library/modules/std/` `#foreign`→`extern`, ~60
-sites).** Phase 6.1 (sqlite) + 6.2 (platform) COMPLETE.
+**PART B — Phase 6.4 (migrate `library/modules/ffi/` `#foreign`→`extern`/`export`,
+~50 sites).** Phase 6.1 (sqlite) + 6.2 (platform) + 6.3 (std) COMPLETE.
 
-- **Phase 6.3** (`refactor`, snapshot diff must be EMPTY): rewrite
-  `library/modules/std/` (socket/thread/fs/time/process/…) `#foreign`→`extern`. Mostly
-  libc fn decls (bare `#foreign;` or `#foreign "csym";`); check for any data-global
-  `#foreign` too. These ARE exercised by the host corpus (fs/process/socket examples),
-  so a non-empty snapshot diff catches a regression directly — STOP and coalesce, don't
-  regen. Transform: `s/ #foreign;/ extern;/` for bare, plus the `#foreign "csym"`/
-  `#foreign LIB "csym"` rename forms where present (verify per-file first like 6.2).
-- **Remaining Phase 6 batches:** 6.4 `library/modules/ffi/` (objc/raylib/objc_block,
-  ~50 — has runtime classes, use the postfix shape like 6.2), 6.5 remaining `library/`+
-  `vendors/`. Then **Phase 7** migrates examples + issues the same way.
+- **Phase 6.4** (`refactor`, snapshot diff must be EMPTY): rewrite
+  `library/modules/ffi/` (objc/objc_block/raylib/sdl3/opengl/stb/…) `#foreign`→`extern`.
+  ⚠ Like platform (NOT std), `ffi/objc.sx` has Obj-C **runtime classes** — use the
+  postfix shape (`#objc_class("X") extern {` for imports, `… export {` for defined),
+  and check each site's shape per-file before bulk-replacing. Verify corpus coverage
+  per module: raylib/stb/sdl3 examples (15xx/12xx) compile on host → corpus validates;
+  any host-uncompiled module (check importers) needs an `sx ir` probe like 6.2.
+- **Remaining Phase 6 batches:** 6.5 remaining `library/`+`vendors/` (math/, other
+  vendors, anything still holding `#foreign`). Then **Phase 7** migrates examples +
+  issues the same way.
 - **6.2 verification note (carry forward):** the `platform/` runtime modules
   (uikit/android/android_jni) are NOT compiled by any marker'd host corpus test — verify
   future platform-adjacent migrations via direct `sx ir` on importers (1610/1606 compile
@@ -323,6 +333,10 @@ Part A ratified (bare / postfix / `⇒ callconv(.c)` / lib-separate). Part B:
   deleted at cutover). Affects only diagnostic wording — IR/behavior identical either way.
 
 ## Log
+- (6.3 std) Migrated 11 `std/` modules (~60 sites): cli/core/fmt/fs/log/net.kqueue/
+  process/socket/thread/time/trace. All fn-decl markers (bare / `libc`|`tlib` LIB ref /
+  `libc "csym"` rename) → `extern …` + 2 comment mentions; no class forms. Host-corpus-
+  exercised → empty snapshot diff validates. Suite green (647/444). `refactor` `59f90d2`.
 - (6.2 platform) Migrated `platform/` (uikit/android/android_jni/sdl3, ~64 sites):
   30 fn `#foreign;`→`extern;`, 34 import classes prefix `#foreign #objc/jni_class`→
   postfix `… extern {`, 4 defined `Sx*` objc classes → `… export {`. Behavior-