plan: aggregate consts (PLAN-CONST-AGG) + file 0116 const-write hole

Array-typed '::' consts as immutable globals (approved design: storage
global + untyped inference + comptime-fold layer + const-write rejection
covering the pre-existing struct-const write crash, issue 0116).

CLAUDE.md

@@ -572,7 +572,8 @@ Wiring a new bundling step:
 | `current/CHECKPOINT-LANG.md` | **Active** LANG progress tracker. Update after every step. |
 | `current/PLAN-ERR.md` | **Active** ERR implementation plan (`!` errors, `try` / `catch` / `or` / `onfail`, return traces). |
 | `current/CHECKPOINT-ERR.md` | **Active** ERR progress tracker. Update after every step. |
-| `current/PLAN-STDLIB.md` | **Active** STDLIB restructure plan (alias carry rule + std/ffi/math layout). Progress tracked in its `## Status` section — no separate checkpoint file. |
+| `current/PLAN-STDLIB.md` | STDLIB restructure plan — **COMPLETE** (alias carry rule + std/ffi/math layout + full namespace tail). |
+| `current/PLAN-CONST-AGG.md` | **Active** aggregate-consts plan (array-typed `::` consts as immutable globals, const-write rejection, comptime folds). Progress tracked in its `## Status` section — no separate checkpoint file. |
 | `implementation_plan.md` | Archive of completed work (closures, protocols, etc.). Do not pick up tasks from here. |
 | `readme.md` | User-facing language overview — **maintained**. Update it whenever a user-facing sx change lands (new/changed syntax, semantics, gating diagnostics, language behavior), per the docs-track-changes rule. |
 | `CLAUDE.md` | This file. Session instructions. |

issues/0116-const-write-not-rejected.md

@@ -0,0 +1,33 @@
+# 0116 — writes through module consts are not rejected (struct-const write bus-errors at runtime)
+
+**Symptom.** Assigning through a module-level constant compiles silently.
+For a struct-literal const the store lands in read-only memory and the
+program crashes at runtime.
+
+- **Observed**: compiles; `Bus error` at runtime on the store.
+- **Expected**: compile-time diagnostic — `cannot assign through constant
+  'WHITE'`.
+
+## Reproduction
+
+```sx
+#import "modules/std.sx";
+
+Color :: struct { r, g, b: s64; }
+WHITE :: Color.{ r = 255, g = 255, b = 255 };
+
+main :: () {
+    WHITE.r = 0;     // compiles; bus error at runtime
+    print("{}\n", WHITE.r);
+}
+```
+
+(Copies are fine and stay fine: `w := WHITE; w.r = 0;` mutates the copy.)
+
+## Fix
+
+Scheduled as **step 2 of `current/PLAN-CONST-AGG.md`** (aggregate consts):
+one rejection rule for assignment/compound-assignment targets whose ROOT
+identifier resolves to a module const (module_const_map author) or a
+const-flagged global (the array consts that plan introduces). Diagnose at
+the assignment site; pin the repro above as a diagnostics example.