fix(tui): skip audio init when no playback device - #51854

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The following comment was made by an LLM, it may be inaccurate:

Field confirmation on Termux (Android 16), patched v2 binary, sounds ON: tool calls complete with no ALSA ghost text. Note: no toast either, which matches the notify path (done-sound is when:always, visual notification is when:blurred, TUI was focused) — so silence here is the correct outcome, not a regression.

Live decision-table check on an audio-less host (stub renderer, real audio module): blurred -> {notification: true, sound: false}, 0 ALSA lines; focused -> {notification: false (by design), sound: false}, 0 ALSA lines. So the patch only ever removes the sound leg; the toast leg is untouched.

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Quick note on the needs:issue label, since it looks like this PR failed the issue-first check. It didn't.

This PR intentionally targets v2, which is where most merged PRs go — 24 of the last 30 merged PRs target v2, vs 3 for dev. v2 is the active line, and this bug affects current users.

The label comes from check-standards, which resolves the issue link through the GraphQL closingIssuesReferences field. That field only resolves when a PR targets the repository's default branch (dev). On a v2-targeted PR it returns 0 even when the body contains Closes #41763 — the link is real (it appears as a cross-reference on the issue), the query just can't see it.

So on v2, the fix/chore/test/docs issue check can't be satisfied structurally. Verified against open PRs: 52037 (dev) returns 1 reference, while 51854, 52038, 52012 and 52040 (all v2) return 0.

Flagging this so the label isn't read as a problem with the PR itself. needs:issue doesn't block merge either — only needs:compliance does, and that one is already cleared.

On the change: it's self-contained — a /dev/snd probe for a PCM playback node before Audio.create runs, so the native backend is never touched on audio-less hosts. Non-Linux and device-present paths are unchanged, and only the sound leg of attention.notify is affected; the notification leg is untouched.