feat(cli): SMALLEST AI brand banner + rename waves group to models

[abhishekmishragithub]

What

• Banner redesign on bare `smallestai`: wordmark now reads SMALLEST AI (was SMALLEST), in the brand blue #3B82F6. Concentric rings sit left-aligned above the wordmark and pulse on an interactive TTY.
• waves → models: the speech command group (TTS/STT/voices) is renamed to `models` in the menu and command. `waves` still works as a hidden back-compat alias.
• Banner rendering extracted to `smallestai/cli/banner.py`.

Behaviour / safety

• Animation only runs on an interactive TTY. Piped output, `CI`, `NO_COLOR`, or `SMALLESTAI_NO_ANIM=1` render a single static frame (no cursor codes, no color when piped).
• The wordmark is 83 columns; terminals narrower than ~87 cols fall back to a compact `SMALLEST AI` text line so nothing wraps.
• No screen-clear: the pulse animates only the ring block in place, then the wordmark prints below.

Tests

• Ring rasterisation shape/width, plus static / compact / animated code paths.
• Existing bare-CLI test updated for the `waves`→`models` menu rename.
• Green locally: ruff 0.16.1 (check + format), mypy 1.13.0, pytest.

Held for review — not for auto-merge.