Add Go and Rust BECs to the catalog

[DataDave-Dev]

Context

The catalog (becs/) ships Python and JS/TS BECs. becwright is language-agnostic,
so adding Go and Rust BECs — built on the generic forbid check, so no new code
is needed — would broaden the catalog and show off the multi-language story.

Proposed approach

Create new .bec.yaml bundles in becs/ using forbid, for example:

• Go: forbid leftover fmt.Println( debug output; flag a stray panic( in
  non-test code.
• Rust: forbid dbg!(; forbid println! debug output; (optionally) flag
  .unwrap() in non-test code.

Follow an existing bundle (e.g. becs/no-debugger-js.bec.yaml) for the format.
Each bundle needs a clear intent and why_it_matters, and paths for the
language (**/*.go, **/*.rs). Add the new entries to becs/README.md.

Acceptance criteria

• Each new bundle imports cleanly (becwright import <file> --yes).
• The new BECs are listed in becs/README.md.

Notes

Good first issue — pure YAML, no code.

Relevant files

becs/, becs/README.md.