docs: close completed plan docs

Author: taedlar

docs/ChangeLog.md

@@ -9,6 +9,7 @@
 - feat: extend `from_json()` to accept `buffer` input for large JSON payloads
 - feat: add optional `PACKAGE_CURL` support with `perform_using()`, `perform_to()`, and `in_perform()` efuns
 - feat: add `c_str()` efun to make C-string truncation an explicit LPC contract
+- feat: harden counted-string comparison and JSON/CURL text-option boundaries to use byte-span semantics and explicit embedded-NUL rejection/conversion rules
 
 #### Documentation
 - doc: add efun docs for `to_json()` and `from_json()`

docs/plan/counted-string.md docs/history/counted-string.mddocs/plan/counted-string.md renamed to docs/history/counted-string.md

@@ -58,6 +58,17 @@ early as possible (compile-time preferred, runtime as backstop).
 | Implementation: JSON boundary contract and tests | complete |
 | Validation: end-to-end LPC/JSON regression matrix | complete |
 
+## Pre-Closing Handoff
+
+As of 2026-04-18, this plan is being closed for the current scoped milestone.
+
+Non-complete items intentionally deferred beyond this closure:
+
+- Broad LPC string-efun hardening outside the narrowed JSON/CURL ingress scope.
+- Future CURL option-surface follow-through, where new text options must preserve
+  the explicit `c_str()` / `to_json()` boundary contract and matching regression
+  coverage.
+
 ## Current State Handoff
 
 As of 2026-04-17 (updated):