docs(core/sort): document all public procedures and Interface type

[dominikake]

Summary

Implements part of #2358 by documenting the core:sort package.

Adds core/strings-style doc comments for the Interface type and all 29 public procedures in core/sort/sort.odin, including Inputs:/Returns: sections and runnable Example:/Output: blocks with exact expected output for every procedure.

The only change is documentation comments — no behavior or logic changes.

Verification

• tests/documentation/documentation_tester.odin (the CI doc test) was run against an all.odin-doc built from a package importing the core packages: Passes: 155, Fails: 0 · Examples verified. All 29 new sort.* examples were generated, compiled, run, and matched their Output: blocks exactly.
• odin doc core/sort renders every public procedure/type with its doc comment.
• No -vet/-strict-style issues (comments only; core:sort is a library with no entry point).

AI assistance disclosure

This PR was drafted with the assistance of an AI coding agent (opencode). The documentation was written from a careful reading of the actual core/sort implementation, and every Example:/Output: block was verified by compiling and running against a built odin compiler, plus the official documentation tester. No code changes were made by the AI.

Refs #2358