refactor: extract _console.py from __init__.py (PR-1/8) (#2474)

* refactor: extract _console.py from __init__.py

Move Rich UI primitives (BANNER, TAGLINE, StepTracker, get_key,
select_with_arrows, console, BannerGroup, show_banner) into a new
src/specify_cli/_console.py module. Re-export all symbols from
__init__.py to preserve the public API. Add regression guard tests.

* refactor(console): improve type annotations and add guard for empty options

- Add module-level docstring documenting the console layer's purpose and
  the dependency-layering rule (no imports from other specify_cli modules)
- Tighten select_with_arrows() signature: options typed as dict[str, str]
  and default_key as str | None to align with repo typing style
- Add early ValueError guard when options is empty, preventing downstream
  ZeroDivisionError / IndexError inside the Live loop

* refactor(console): improve type safety and code quality in _console.py

- Add Callable import from collections.abc for precise callback typing
- Annotate StepTracker._refresh_cb as Callable[[], None] | None
- Add parameter/return types to attach_refresh()
- Use explicit keyword form typer.Exit(code=1) across all error exits
- Add blank line between StepTracker class and get_key() (PEP 8)
- Add regression test for select_with_arrows() raising ValueError on
  empty options dict

* style(cli): add __all__ declaration to fix Ruff F401 lint warnings

- Add explicit __all__ for intentional re-exports (BANNER, TAGLINE, get_key)
- Prevent F401 unused import errors in CI lint checks
- Maintain backward compatibility for external imports

* Preserve public console imports

The CLI package intentionally re-exports console helpers for compatibility, so __all__ must track that public surface instead of narrowing star imports to a partial set.

Constraint: Existing tests import console helpers directly from specify_cli

Rejected: Remove __all__ entirely | keeping an explicit export list documents the intended compatibility surface

Confidence: high

Scope-risk: narrow

Directive: Keep __all__ synchronized when adding or removing specify_cli public re-exports

Tested: uv run pytest tests/test_console_imports.py -q

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* style(cli): use explicit re-export syntax to fix ruff F401 warnings

Use `X as X` form for BANNER, TAGLINE, and get_key imports
to mark them as intentional public re-exports and silence
ruff F401 lint errors.

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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>