docs: consolidate troubleshooting into the MDX docs site + status updates

- Delete docs/TROUBLESHOOTING.md; the canonical troubleshooting guide now
  lives under docs/content/docs/overview/troubleshooting.mdx so it's served
  from docs.voicebox.sh alongside the rest of the docs.
- CONTRIBUTING.md + README.md: repoint "Troubleshooting" references to the
  new MDX path. README gets a top-level callout so users hit the guide
  before filing an issue.
- PROJECT_STATUS.md: refresh issue/PR counts, document the flash-attn
  warning (cosmetic on all platforms; CUDA-only, fallback is PyTorch SDPA
  which is near-FA2 on Ampere+) with per-platform context + community
  Windows wheels + SageAttention/xformers alternatives, add WebAudio
  audio-session bug note (tracked separately in PR #486), and expand the
  Qwen 0.6B→1.7B MLX fallback explanation for triage.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

README.md

@@ -33,7 +33,8 @@
   <a href="https://docs.voicebox.sh">Docs</a> •
   <a href="#download">Download</a> •
   <a href="#features">Features</a> •
-  <a href="#api">API</a>
+  <a href="#api">API</a> •
+  <a href="docs/content/docs/overview/troubleshooting.mdx">Troubleshooting</a>
 </p>
 
 <br/>
@@ -91,6 +92,8 @@ Voicebox is a **local-first voice cloning studio** — a free and open-source al
 
 > **Linux** — Pre-built binaries are not yet available. See [voicebox.sh/linux-install](https://voicebox.sh/linux-install) for build-from-source instructions.
 
+> **Having trouble?** See the [Troubleshooting Guide](docs/content/docs/overview/troubleshooting.mdx) for common install, generation, model-download, and GPU issues.
+
 ---
 
 ## Features