feat(cli): Phase D — compile-eph / compile-affine aliases (closes #36) (#123)

clap visible aliases so the CLI can be invoked as `compile-eph` and
`compile-affine`, both routing to the `compile` subcommand. Probed by
hypatia's build-gossamer-gui.yml workflow.

Salvaged from the diverged ephapax v2-grammar branch onto current main.
The superseded v2 extern/grammar phases (A/B/C/E/F-H/I/J) are NOT
included — upstream main already ships a more complete extern
implementation with a different API. The single test fixture
`tests/v2-grammar/fixtures/ extern-callsite.eph` is carried from the
dropped Phase B commit (6f7f316) so the Phase D acceptance test is
self-contained; verified to compile to valid wasm on current main via
the new aliases.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath