Added AI skills

.agents/skills/zod/references/schema-coercion-for-form-data.md

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+---
+title: Use Coercion for Form and Query Data
+impact: CRITICAL
+impactDescription: Form data and query params are always strings; without coercion, z.number() rejects "42" and z.boolean() rejects "true"
+tags: schema, coerce, forms, query-params
+---
+
+## Use Coercion for Form and Query Data
+
+HTML forms and URL query parameters always transmit data as strings. Using `z.number()` on form data will fail because `"42"` is not a number. Use `z.coerce.number()` to automatically convert strings to the correct type.
+
+**Incorrect (no coercion for form data):**
+
+```typescript
+import { z } from 'zod'
+
+const searchSchema = z.object({
+  query: z.string(),
+  page: z.number(),  // Expects actual number
+  limit: z.number(),
+  showDeleted: z.boolean(),  // Expects actual boolean
+})
+
+// Form data / query params are strings
+const formData = new URLSearchParams('query=test&page=1&limit=10&showDeleted=true')
+const params = Object.fromEntries(formData)
+// { query: 'test', page: '1', limit: '10', showDeleted: 'true' }
+
+searchSchema.parse(params)
+// ZodError: Expected number, received string at "page"
+// ZodError: Expected number, received string at "limit"
+// ZodError: Expected boolean, received string at "showDeleted"
+```
+
+**Correct (using coercion):**
+
+```typescript
+import { z } from 'zod'
+
+const searchSchema = z.object({
+  query: z.string(),
+  page: z.coerce.number().int().positive().default(1),
+  limit: z.coerce.number().int().min(1).max(100).default(10),
+  showDeleted: z.coerce.boolean().default(false),
+})
+
+// Form data / query params are strings
+const formData = new URLSearchParams('query=test&page=1&limit=10&showDeleted=true')
+const params = Object.fromEntries(formData)
+
+const result = searchSchema.parse(params)
+// { query: 'test', page: 1, limit: 10, showDeleted: true }
+// Types are correct: number, number, boolean
+```
+
+**Available coercion types:**
+
+```typescript
+z.coerce.string()  // Converts anything to string via String(value)
+z.coerce.number()  // Converts via Number(value), NaN fails validation
+z.coerce.boolean()  // Truthy/falsy conversion
+z.coerce.bigint()  // Converts via BigInt(value)
+z.coerce.date()  // Converts via new Date(value)
+```
+
+**Coercion edge cases:**
+
+```typescript
+// z.coerce.number() behavior
+z.coerce.number().parse("42")  // 42
+z.coerce.number().parse("")  // 0 (empty string becomes 0!)
+z.coerce.number().parse("abc")  // ZodError (NaN fails)
+
+// z.coerce.boolean() behavior
+z.coerce.boolean().parse("true")  // true
+z.coerce.boolean().parse("false")  // true! (non-empty string is truthy)
+z.coerce.boolean().parse("")  // false
+z.coerce.boolean().parse("0")  // true! (non-empty string)
+
+// For strict boolean parsing from strings:
+const strictBooleanSchema = z.enum(['true', 'false']).transform(v => v === 'true')
+```
+
+**When NOT to use this pattern:**
+- When receiving JSON payloads (already typed correctly)
+- When you want strict type checking without conversion
+
+Reference: [Zod API - Coercion](https://zod.dev/api#coercion)