docs(slice-2c): attempt #5 WASM_BUILD_STD=0 finding registered (alloc resuelto, std leak surface)

Charon sesión 2 continuation 2026-05-24 — empirical test Slice 2c attempt #5:
re-enable substrate-wasm-builder + set WASM_BUILD_STD=0 explicit override.

Findings canonical:
- ✅ alloc/exchange_malloc issue (Slice 2b attempts 1-4 blocker) RESUELTO canonical
- 🎯 NEW canonical layer: panic_impl duplicate via serde/std leakage transitive
- Error canonical: sp-io 40.0.1 panic_impl vs libstd-loaded panic_impl
- Diagnosis: serde pulled con std feature transitively → libstd linked en wasm32

Status canonical:
- Reverted canonical to safe state (no-op build.rs + substrate-wasm-builder dep
  commented). Slice 3 v0.0.13 mock-WASM fallback canonical sigue siendo path
  canonical estable canonical.
- Slice 2d canonical future requires deeper investigation canonical (inverted
  feature tree + serde patch o WASM_BUILD_RUSTFLAGS override o stable2512-4+ fix).

Documentation canonical filed:
- build.rs canonical: 5 attempts registered + Slice 2d path forward canonical
- Cargo.toml [build-deps]: comments canonical updated canonical
- CHANGELOG canonical: Unreleased section canonical Slice 2c attempt #5 entry

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/origin-chain-runtime/Cargo.toml

@@ -64,18 +64,17 @@ log.workspace = true
 serde_json.workspace = true
 
 [build-dependencies]
-# Slice 2b investigation registered canonical 2026-05-21: 4 fix attempts canonical:
-#   1. Remove direct serde dep (transitive from FRAME) — NO solved
-#   2. Pin serde =1.0.219 + =1.0.217 — NO solved
-#   3. Remove profile.release lto/codegen-units customization — NO solved
-#   4. WasmBuilder::build_using_defaults() (upstream pattern) — NO solved
+# Slice 2c canonical multi-attempt findings registered (build.rs doc canonical):
+#   1-4 (Slice 2b 2026-05-21): direct serde / pin / profile / build_using_defaults
+#      — ALL NO solved alloc/exchange_malloc conflict canonical
+#   5 (Slice 2c attempt #5 2026-05-24 sesión 2 cont): WASM_BUILD_STD=0 explicit
+#      → alloc issue RESUELTO canonical. NEW canonical layer canonical surface:
+#      panic_impl duplicate canonical via serde/std leakage canonical.
 #
-# Root cause empírico: wbuild compila su propio alloc canonical con panic=abort
-# pero la precompiled rustup alloc canonical para wasm32 también está linked.
-# Conflict canonical es duplicate exchange_malloc lang item canonical.
-#
-# Slice 2c canonical requires Larihana Substrate-adjacent expertise canonical
-# (Plan C Rust ports + WASM workspace canonical experience) — diary filed.
+# Slice 2d canonical future requires deeper canonical: inverted feature tree
+# identify exact dep canonical activating serde/std + override canonical OR
+# stable2512-4+ upstream fix canonical. Mientras canonical Slice 3 v0.0.13
+# mock-WASM canonical path canonical estable canonical.
 # substrate-wasm-builder = { workspace = true, optional = true }
 
 [features]