Updated Readme files

pkg/writers/yaml/README.md

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+# YAML Writer
+
+Generates database schema definitions in YAML format.
+
+## Overview
+
+The YAML Writer converts RelSpec's internal database model representation into YAML format, providing a human-readable, structured representation of the database schema.
+
+## Features
+
+- Generates RelSpec's canonical YAML schema format
+- Human-readable alternative to JSON
+- Complete schema representation including:
+  - Databases and schemas
+  - Tables, columns, and data types
+  - Constraints (PK, FK, unique, check)
+  - Indexes
+  - Relationships
+  - Views and sequences
+- Supports comments
+- Ideal for manual editing and configuration
+
+## Usage
+
+### Basic Example
+
+```go
+package main
+
+import (
+    "git.warky.dev/wdevs/relspecgo/pkg/models"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers/yaml"
+)
+
+func main() {
+    options := &writers.WriterOptions{
+        OutputPath: "schema.yaml",
+    }
+
+    writer := yaml.NewWriter(options)
+    err := writer.WriteDatabase(db)
+    if err != nil {
+        panic(err)
+    }
+}
+```
+
+### CLI Examples
+
+```bash
+# Export PostgreSQL database to YAML
+relspec --input pgsql \
+  --conn "postgres://localhost/mydb" \
+  --output yaml \
+  --out-file schema.yaml
+
+# Convert GORM models to YAML
+relspec --input gorm --in-file models.go --output yaml --out-file schema.yaml
+
+# Convert JSON to YAML
+relspec --input json --in-file schema.json --output yaml --out-file schema.yaml
+```
+
+## Generated YAML Example
+
+```yaml
+name: myapp
+database_type: postgresql
+source_format: pgsql
+schemas:
+  - name: public
+    tables:
+      - name: users
+        schema: public
+        columns:
+          id:
+            name: id
+            table: users
+            schema: public
+            type: bigint
+            not_null: true
+            is_primary_key: true
+            auto_increment: true
+            sequence: 1
+          username:
+            name: username
+            table: users
+            schema: public
+            type: varchar
+            length: 50
+            not_null: true
+            sequence: 2
+          email:
+            name: email
+            table: users
+            schema: public
+            type: varchar
+            length: 100
+            not_null: true
+            sequence: 3
+        constraints:
+          pk_users:
+            name: pk_users
+            type: PRIMARY KEY
+            table: users
+            schema: public
+            columns:
+              - id
+          uq_users_username:
+            name: uq_users_username
+            type: UNIQUE
+            table: users
+            schema: public
+            columns:
+              - username
+        indexes:
+          idx_users_email:
+            name: idx_users_email
+            table: users
+            schema: public
+            columns:
+              - email
+            unique: false
+            type: btree
+
+      - name: posts
+        schema: public
+        columns:
+          id:
+            name: id
+            type: bigint
+            not_null: true
+            is_primary_key: true
+            sequence: 1
+          user_id:
+            name: user_id
+            type: bigint
+            not_null: true
+            sequence: 2
+          title:
+            name: title
+            type: varchar
+            length: 200
+            not_null: true
+            sequence: 3
+          content:
+            name: content
+            type: text
+            not_null: false
+            sequence: 4
+        constraints:
+          fk_posts_user_id:
+            name: fk_posts_user_id
+            type: FOREIGN KEY
+            table: posts
+            schema: public
+            columns:
+              - user_id
+            referenced_table: users
+            referenced_schema: public
+            referenced_columns:
+              - id
+            on_delete: CASCADE
+            on_update: NO ACTION
+        indexes:
+          idx_posts_user_id:
+            name: idx_posts_user_id
+            columns:
+              - user_id
+            unique: false
+            type: btree
+    views: []
+    sequences: []
+```
+
+## Schema Structure
+
+The YAML format mirrors the JSON structure with human-readable syntax:
+
+- Database level: `name`, `database_type`, `source_format`, `schemas`
+- Schema level: `name`, `tables`, `views`, `sequences`
+- Table level: `name`, `schema`, `columns`, `constraints`, `indexes`
+- Column level: `name`, `type`, `length`, `not_null`, etc.
+- Constraint level: `name`, `type`, `columns`, foreign key details
+- Index level: `name`, `columns`, `unique`, `type`
+
+## Advantages Over JSON
+
+- More human-readable
+- Easier to edit manually
+- Supports comments
+- Less verbose (no braces/brackets)
+- Better for configuration files
+- Natural indentation
+
+## Use Cases
+
+- **Configuration** - Schema as configuration
+- **Documentation** - Human-readable schema docs
+- **Version Control** - Easier to read diffs
+- **Manual Editing** - Easier to modify by hand
+- **Code Generation** - Template-friendly format
+
+## Notes
+
+- Output is properly indented (2 spaces)
+- Preserves all schema metadata
+- Can be round-tripped with YAML reader
+- Compatible with YAML 1.2
+- More readable than JSON for large schemas
+- Ideal for documentation and manual workflows