实现指令编解码与反汇编，冻结 disasm 格式。

- Encode.h/Encode.cpp：encode/decode 往返 + disasm 一行文本
- 指令与映像.md 新增反汇编格式表（9 种形态 + 未知操作码）
- Op.h STORE_* 注释对齐 disasm（rs, slot 寄存器在前）

isa/include/isa/Encode.h

@@ -0,0 +1,31 @@
+/**
+ * @file Encode.h
+ * @brief 指令编解码与反汇编
+ * @author 
+ * @date 2026-08-19
+ */
+
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+
+#include "isa/Instr.h"
+#include "isa/Op.h"
+
+namespace isa {
+    // 解码后的字段视图
+    struct Decoded {
+        Op op;
+        uint8_t rd;
+        uint8_t a;
+        uint8_t b;
+    };
+
+    // 编解码往返：encode(decode(w)) == w
+    Instr encode(Decoded d);
+    Decoded decode(Instr w);
+
+    // 反汇编一行文本，写入 out，至多 cap 字节（含 '\0'）。格式见 Doc/isa/指令与映像.md。
+    void disasm(Instr w, char* out, size_t cap);
+}

isa/include/isa/Op.h

@@ -32,11 +32,11 @@ namespace isa {
         JT = 16,           // JT r, offset
         JF = 17,           // JF r, offset
         LOAD_I = 18,       // LOAD_I rd, slot
-        STORE_Q = 19,      // STORE_Q slot, rs
+        STORE_Q = 19,      // STORE_Q rs, slot
         LOAD_M = 20,       // LOAD_M rd, slot
-        STORE_M = 21,      // STORE_M slot, rs
+        STORE_M = 21,      // STORE_M rs, slot
         LOAD_GLOBAL = 22,  // LOAD_GLOBAL rd, slot
-        STORE_GLOBAL = 23, // STORE_GLOBAL slot, rs
+        STORE_GLOBAL = 23, // STORE_GLOBAL rs, slot
         CAL_TON = 24,      // CAL_TON instance_slot
         CAL_TOF = 25,      // CAL_TOF instance_slot
         CAL_CTU = 26,      // CAL_CTU instance_slot