fix model download examples

[eecczz]

Summary

This fixes the model download examples in the STT and TTS usage docs.

• Use the ASR task when checking whether the STT model was installed
• Print model IDs directly with jq -r '.data[]?.id'
• Make the TTS install check match the Kokoro model ID returned by the models API

Closes #617
Closes #618

Why

The current STT example checks installed models with --task text-to-speech, so users following the speech-to-text docs will not see the downloaded ASR model.

The updated examples also make the jq output easier to copy and verify by printing matching model IDs directly instead of JSON arrays.

Verification

• uv run mkdocs build --strict

Note: I also tried running Ruff on the modified files as requested by the contributor instructions, but these files are Markdown, so Ruff attempts to parse them as Python and reports syntax errors.