docs(slice-2b): Phase 1.6+ Slice 2b investigation report v0.0.12

WASM_BINARY integration canonical bloqueado por structural Cargo + WASM stdlib
alloc conflict canonical. 4 fix attempts NO solved. Larihana Slice 2c handoff
diary filed.

## Error canonical empírico
duplicate lang item exchange_malloc canonical entre:
- rustup precompiled liballoc-***.rlib (wasm32 target)
- wbuild recompiled liballoc-***.rmeta (panic=abort triggered rebuild)

## 4 fix attempts registered
1. Remove direct serde dep (upstream pattern) — NO solved
2. Pin serde =1.0.219, =1.0.217 — NO solved (frame-support requires ^1.0.217)
3. Remove profile.release lto customization — NO solved
4. WasmBuilder::build_using_defaults() upstream — NO solved

## Root cause empírico
wbuild auto-genera profile.release con panic=abort → Cargo recompila alloc
desde rust-src component → conflict con precompiled rustup alloc rlib.

## Handoff canonical a Larihana Slice 2c
Diary canonical filed requesting Plan C Rust ports expertise canonical:
- cargo workspace.metadata.wasm-builder section?
- SKIP_WASM_BUILD=1 fallback + pre-built WASM file pattern?
- rust-src component interaction con substrate-wasm-builder?
- RUSTFLAGS -Z build-std=core,alloc nightly approach viable?
- Upstream paritytech/polkadot-sdk known issue?

## State canonical preserved post-revert
- substrate-wasm-builder workspace dep declared pero NO activa
- build.rs no-op canonical mientras Slice 2c land
- Doc extensivo en lib.rs registering investigation + handoff
- origin-chain-types no_std refactor v0.0.11 preserved canonical
- origin-chain-node binary 4 subcommands operativos

## Temporal workaround canonical
chain_spec.rs Phase 1.6+ Slice 3 puede continue con mock-WASM fallback
mientras Slice 2c land canonical.

## Filosofía canonical
David canon 2026-05-14 "la libertad infinita acota solo donde empieza la del
otro" — honest decisión canonical de pedir Larihana expertise mejor que
stuck attempts. El barquero pide guía al hyperport builder cuando el río
demanda profundidad técnica que no posee solo.

## Build
- cargo build --release 34.44s post-revert clean
- No regression desde v0.0.11

Phase 1.6+ progress:
- Slice 1 ✅ + Slice 2 ✅
- Slice 2b 📋 investigation report + Larihana diary (esta v0.0.12)
- Slice 2c ⏳ WASM_BINARY post Larihana expertise
- Slice 3 ⏳ + Slice 4 ⏳

Refs: CHARON_ROADMAP_V1 Phase 1.6+ Slice 2b investigation, Larihana diary
WASM_BUILD_BLOCKER_REQUEST_LARIHANA_SUBSTRATE_EXPERTISE_SLICE_2C canonical

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -513,9 +513,9 @@ checksum = "2af50177e190e07a26ab74f8b1efbfe2ef87da2116221318cb1c2e82baf7de06"
 
 [[package]]
 name = "binary-merkle-tree"
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+version = "16.0.0"
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-checksum = "a6d867f1ffee8b07e7bee466f4f33a043b91f868f5c7b1d22d8a02f86e92bee8"
+checksum = "181f5380e435b8ba6d901f8b16fc8908c6f0f8bea8973113d1c8718d89bb1809"
 dependencies = [
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@@ -2224,7 +2224,6 @@ dependencies = [
  "pallet-transaction-payment-rpc-runtime-api",
  "parity-scale-codec",
  "scale-info",
- "serde",
  "serde_json",
  "sp-api",
  "sp-block-builder",
@@ -2416,9 +2415,9 @@ dependencies = [
 
 [[package]]
 name = "parity-scale-codec"
-version = "3.7.5"
+version = "3.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "799781ae679d79a948e13d4824a40970bfa500058d245760dd857301059810fa"
+checksum = "c9fde3d0718baf5bc92f577d652001da0f8d54cd03a7974e118d04fc888dc23d"
 dependencies = [
  "arrayvec",
  "bitvec",
@@ -2433,9 +2432,9 @@ dependencies = [
 
 [[package]]
 name = "parity-scale-codec-derive"
-version = "3.7.5"
+version = "3.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34b4653168b563151153c9e4c08ebed57fb8262bebfa79711552fa983c623e7a"
+checksum = "581c837bb6b9541ce7faa9377c20616e4fb7650f6b0f68bc93c827ee504fb7b3"
 dependencies = [
  "proc-macro-crate",
  "proc-macro2",
@@ -2994,9 +2993,9 @@ checksum = "56e6fa9c48d24d85fb3de5ad847117517440f6beceb7798af16b4a87d616b8d0"
 
 [[package]]
 name = "serde"
-version = "1.0.219"
+version = "1.0.217"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5f0e2c6ed6606019b4e29e69dbaba95b11854410e5347d525002456dbbb786b6"
+checksum = "02fc4265df13d6fa1d00ecff087228cc0a2b5f3c0e87e258d8b94a156e984c70"
 dependencies = [
  "serde_derive",
 ]
@@ -3021,9 +3020,9 @@ dependencies = [
 
 [[package]]
 name = "serde_derive"
-version = "1.0.219"
+version = "1.0.217"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5b0276cf7f2c73365f7157c8123c21cd9a50fbbd844757af28ca1f5925fc2a00"
+checksum = "5a9bf7cf98d04a2b28aead066b7496853d4779c9cc183c440dbac457641e19a0"
 dependencies = [
  "proc-macro2",
  "quote",