feat: add SchemaBuilder fluent API

[jhamon]

Summary

Add SchemaBuilder class that provides a fluent, chainable API for building index schemas.

Closes SDK-102

API

Method	Description
.text(name, ...)	Add text field with filterable, full_text_searchable options
.integer(name, ...)	Add integer field with filterable option
.float(name, ...)	Add float field with filterable option
.dense_vector(name, dimension, metric, ...)	Add dense vector field
.sparse_vector(name, ...)	Add sparse vector field
.semantic_text(name, model, field_map, ...)	Add semantic text field with inference
.build()	Returns the final schema dictionary

Usage Example

from pinecone import SchemaBuilder

schema = (SchemaBuilder()
    .text("title", full_text_searchable=True)
    .integer("year", filterable=True)
    .dense_vector("embedding", dimension=1536, metric="cosine")
    .build())

pc.create_index(name="my-index", schema=schema, ...)

Test Plan

• Unit tests for each field type method (18 tests)
• Tests for method chaining
• Tests for empty schema validation
• Tests for field overwriting behavior
• mypy type checking passes

---

Note

Low Risk
Low risk, additive change that introduces a new helper class and exports it via existing lazy-import/public-module surfaces without modifying request/serialization logic.

Overview
Introduces SchemaBuilder, a fluent, chainable helper for building index schema dictionaries from existing field types (TextField, DenseVectorField, SemanticTextField, etc.), including validation that prevents building an empty schema.

Exports SchemaBuilder via pinecone.db_control.models and the top-level pinecone lazy imports, and adds focused unit tests for each field type, option serialization, chaining behavior, and overwrite semantics.

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Duplicated module loading logic in test file

Low Severity

The _load_schema_builder_module() function duplicates the schema_fields loading logic (lines 12-27) that already exists in test_schema_fields.py as _load_schema_fields_module(). Both implementations create a module, set its file path, register it in sys.modules, and exec the file contents. This duplicated workaround code increases maintenance burden - if the loading approach needs to change, it must be updated in multiple places.