docs: update README for async entry, entering status, 50ms scan

- Architecture diagram: async goroutine entry path
- Trading Logic: async entry, entering status protection
- Config note: floor rounding on both exchanges

README.md

@@ -24,11 +24,12 @@ PriceStore ─────────┼─────────────
                  └─────────┬─────────┘
                            │
            ┌───────────────▼────────────────┐
-           │   Trader (trading logic only)   │
-           │  TryEntry / Tick / Exit        │
-           │  Maker fees, scale-in, stop    │
-           │  Synchronous entry (no goroutine)│
-           │  NO display/stat calculations  │
+           │   Trader                        │
+           │   TryEntry (async goroutine)    │
+           │   → placeOrder (REST)           │
+           │   Tick / Exit / Scale-in        │
+           │   Maker fees only               │
+           │   NO display/stat calculations  │
            └───────────────┬────────────────┘
                            │
                  ┌─────────▼─────────┐
@@ -97,7 +98,7 @@ Then open [http://localhost:8888](http://localhost:8888) for the Web dashboard.
 | `BITGET_API_KEY` / `BITGET_API_SECRET` / `BITGET_PASSPHRASE` | — | Bitget API credentials (test mode skips) |
 | `HL_PRIVATE_KEY` / `HL_ADDRESS` | — | HyperLiquid wallet credentials (test mode skips) |
 
-> **Note:** Scan interval is fixed at **50ms**. At this rate the scanner catches every HyperLiquid ~200ms push without any jitter.
+> **Note:** Scan interval is fixed at **50ms** (not configurable). Order sizes round DOWN (`math.Floor`) on both Bitget and HyperLiquid for consistency.
 
 ## Fee Model
 
@@ -115,8 +116,10 @@ Round trip (2 legs entry + 2 legs exit): **0.07%** total fees.
 1. **Scanner** runs every 50ms, checks all 6 coins for BG ↔ HL spread
 2. **Entry** when net profit ≥ `TRADE_THRESHOLD` (after full round-trip fees)
    - Uses scan-time prices directly (no re-read from store to avoid WS jitter)
-   - Synchronous execution in the scanner tick (no goroutine delay)
+   - **Async goroutine** — `TryEntry` returns immediately, `executeEntry` runs in background
    - Direction sanity check (0.1% tolerance) prevents entry on reversed spreads
+   - `entering` status prevents `checkExit` / `checkScaleIn` during leg placement
+   - `entering` map prevents duplicate entries on the same coin
 3. **Scale-in** adds another leg-worth when spread widens another 0.10%
 4. **Exit** conditions (whichever hits first):
    - Spread converges to ≤ 0.02% → **价差收敛，止盈平仓**