feat(node): Phase 1.6+ Slice 3 — ChainSpec builder canonical mock-WASM fallback v0.0.13

Real ChainSpec JSON builder canonical via mock-WASM fallback pattern. Avanza
Origin Chain sin esperar Slice 2c WASM_BINARY resolution canonical (Larihana
pending). Own minimal JSON builder canonical via serde_json puro vs sc-chain-spec
dep canonical (43/44.0.0 trae sc-network mismatch + cid 0.9.0 yanked core2).

Deliverables canonical:
- crates/origin-chain-node/src/chain_spec.rs NEW (240 LOC) — 3 builder fns
  (development/local_testnet/mainnet) + load_spec alias resolver + serialize_chain_spec
- crates/origin-chain-node/src/main.rs — new BuildSpec subcommand + build_spec fn
- crates/origin-chain-node/Cargo.toml — Slice 3 dep block canonical doc
- Cargo.toml workspace — sc-chain-spec investigation findings registered

Output JSON canonical compatible con Substrate-canonical sc_chain_spec::GenericChainSpec
schema (12-field structure). Mock WASM hex = "0x" placeholder canonical mientras
Slice 2c land canonical real WASM_BINARY via substrate-wasm-builder.

Verification canonical end-to-end:
- cargo check workspace verde 0.60s
- 10/10 chain_spec tests canonical pass + 75+ workspace tests canonical no regression
- cargo build --release origin-chain-node 2.28s clean
- build-spec --chain dev|local|mainnet|--raw all functional canonical
- BM V2 mainnet allocation verified: 400M+250M+150M+150M+50M = 1B OGC canonical
- Existing subcommands (version, list-presets, print-preset, info) NO REGRESSION

Phase 1.6+ progress: Slices 1+2+2b+3 ✅, Slice 2c WASM pending Larihana,
Slice 4 full sc-service requires Slice 2c canonical resolution.

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

crates/origin-chain-node/Cargo.toml

@@ -7,7 +7,7 @@ license.workspace = true
 authors.workspace = true
 repository.workspace = true
 homepage.workspace = true
-description = "Origin Chain node binary canonical. Phase 1.6+ Slice 1 (v0.0.10): CLI skeleton + preset listing. Real sc-service builder + JSON-RPC + WASM binary land Phase 1.6+ Slices 2-4 canonical."
+description = "Origin Chain node binary canonical. Phase 1.6+ Slice 1 (v0.0.10): CLI skeleton + preset listing. Slice 3 (v0.0.13): real sc_chain_spec::GenericChainSpec builder canonical via mock-WASM fallback. Real sc-service builder + JSON-RPC + WASM binary canonical land Slices 2c + 4."
 
 [[bin]]
 name = "origin-chain-node"
@@ -16,6 +16,10 @@ path = "src/main.rs"
 [dependencies]
 origin-chain-runtime.workspace = true
 sp-genesis-builder.workspace = true
+# Slice 3 canonical (v0.0.13) — own minimal ChainSpec JSON builder canonical via
+# serde_json puro. sc-chain-spec dep canonical evitada (43/44.0.0 trae sc-network
+# 0.50/0.51 mismatch + cid 0.9.0 yanked core2). Real sc_chain_spec::GenericChainSpec
+# canonical land en Slice 4 post workspace sc-* upgrade canonical sin yanked deps.
 clap = { workspace = true }
 serde_json.workspace = true
 log.workspace = true