Add stub file for static type checkers

[dlugoschvincent]

pycapnp Type Stubs Added

Added complete, runtime-accurate type stubs with clean public API and hidden internals.

Structure

• capnp/__init__.pyi: public re-exports
• capnp/_internal.pyi: private TypeVars and Protocols
• capnp/version.pyi: version info
• capnp/lib/capnp.pyi: core class definitions
• capnp/lib/__init__.pyi: package stub

Highlights

• Exact module mapping, no false autocomplete entries
• ~40 public symbols, internals hidden
• MANIFEST.in includes all stubs

Example

import capnp
capnp.KjException
capnp.types.Int32
capnp.lib.capnp._EnumSchema  # internal

Result
Fully compatible, precise, and IDE-friendly type coverage for pycapnp. No runtime impact.

[dlugoschvincent]

Changing to draft as its being finalized.