chore: import upstream snapshot with attribution

skills/tinystruct-patterns/references/database.md

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+# tinystruct Database Persistence
+
+## When to Use
+
+Use the built-in ORM-like data layer for database operations. It provides a lightweight alternative to JPA/Hibernate using POJOs extending `AbstractData` and XML mapping files.
+
+## How It Works
+
+### Architecture
+
+Each table is represented by:
+1. **Java POJO**: Extends `AbstractData`, provides getters/setters and `setData(Row)`.
+2. **Mapping XML**: `ClassName.map.xml` in resources, binding Java fields to DB columns.
+
+#### Key Base Class: `AbstractData`
+Provides CRUD methods:
+- `append()` / `appendAndGetId()`
+- `update()`
+- `delete()`
+- `findAll()` / `findOneById()` / `findOneByKey(key, value)`
+- `findWith(where, params)`
+- `find(SQL, params)`
+
+### POJO Generation (CLI)
+
+Introspect a live database table to produce the POJO and mapping file.
+
+#### Configuration
+`application.properties`:
+```properties
+driver=com.mysql.cj.jdbc.Driver
+database.url=jdbc:mysql://localhost:3306/mydb
+database.user=root
+database.password=secret
+```
+
+#### Command
+```bash
+# Interactive mode
+bin/dispatcher generate
+
+# Specify table
+bin/dispatcher generate --tables users
+```
+
+## Examples
+
+### CRUD Operations
+```java
+// CREATE
+User user = new User();
+user.setUsername("james");
+user.append();
+
+// READ
+User user = new User();
+user.setId(42);
+user.findOneById();
+
+// UPDATE
+user.setEmail("new@example.com");
+user.update();
+
+// DELETE
+user.delete();
+```
+
+### Querying with Conditions
+```java
+User user = new User();
+Table results = user.findWith("username LIKE ?", new Object[]{"%jam%"});
+
+// Fluent Condition Builder
+Condition condition = new Condition();
+condition.setRequestFields("id,username");
+Table filtered = user.find(
+    condition.select("`users`").and("email LIKE ?").orderBy("id DESC"),
+    new Object[]{"%@example.com"}
+);
+```
+
+### Mapping XML Structure
+`User.map.xml`:
+```xml
+<mapping>
+  <class name="User" table="users">
+    <id name="Id" column="id" increment="true" generate="false" length="11" type="int"/>
+    <property name="username" column="username" length="50" type="varchar"/>
+    <property name="email" column="email" length="100" type="varchar"/>
+  </class>
+</mapping>
+```
+
+## Important Rules
+
+1. **File Placement**: The mapping XML **must** mirror the POJO's package path under `src/main/resources/`.
+2. **Naming**: Table names are singularized for class names (`users` → `User`). Underscored columns become camelCase fields (`created_at` → `createdAt`).
+3. **Setters**: Use `setFieldAsXxx` methods (e.g., `setFieldAsString`) in setters to sync state with the internal field map.
+4. **Id Field**: The primary key field in Java is always named `Id` (inherited from `AbstractData`).