docs: Add WASM adaptations guide and update README

Author: EthanYuan

README.md

@@ -1,6 +1,11 @@
 Rust-Lightning
 ==============
 
+> ​**WASM Adaptation Notice**  
+> This fork includes WebAssembly-specific changes.  
+> See [adaptations guide](./WASM-ADAPTATIONS.md) for details.  
+> ──────────────────────────────────
+
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WASM-ADAPTATIONS.md

@@ -0,0 +1,39 @@
+# WASM Adaptations Guide
+
+**Branch**: [`wasm-adapt`](https://github.com/utxostack/rust-lightning/tree/wasm-adapt)  
+
+## Core Modifications
+
+```diff
+- use std::time::{SystemTime, UNIX_EPOCH, Instant};
++ use lightning_common::{SystemTime, UNIX_EPOCH, Instant};
+```
+
+## Scope
+
+- Applies to all source files ​**except** test modules
+- Centralized in [`lightning-common`](./lightning-common/src/lib.rs) crate
+
+---
+
+## ​Maintenance Workflow
+
+Upgrade Example (v0.0.125)
+
+
+1. ​**Rebase to upstream version**  
+   ```bash
+   git checkout wasm-adapt
+   git rebase --onto v0.0.125
+   ```
+
+2. ​**Verify adaptation integrity**  
+
+   - Comprehensive code review to ensure that WASM-specific changes have not been missed
+   - Perform necessary integration tests
+
+3. **​Tag**
+
+   ```bash
+   git tag wasm-v0.0.125
+   ```