feat(m14): AI assistant — explain diagnostics, opt-in (Ollama or Claude) — 0.27.0

New optional module (D24): explains the collected findings in plain language,
contacted ONLY on an explicit user action (never automatic).

- core/ai.py: provider chosen explicitly (no default) — ollama (local) or claude
  (Anthropic Messages API via stdlib urllib; key in keyring). Grounded prompt;
  HTTP error parsing; one-shot (no thinking/caching — snappy).
- core/ai_knowledge.py: curated reference KB (Xid/SMART/Proton/tunables),
  exact keyword/code match ("RAG-lite", no embeddings) injected into the prompt —
  lifts local models, sharpens Claude. No fine-tuning.
- config: ai_provider/ai_model/ai_endpoint + keyring-backed AI key (generalized
  the token keyring helpers).
- GUI: Settings → AI assistant (provider radios, model/endpoint/key, Save/Test);
  "Explain with AI" button on the diagnostic dialog (consent prompt for cloud).
- CLI: `rigdoctor ai status|test|explain`.
- Docs: D24, SPEC/MODULES/ROADMAP (Phase 7); tests for providers/grounding/parse.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/MODULES.md

@@ -20,6 +20,7 @@ Status: ⬜ not started · 🟦 designing · 🟨 in progress · ✅ done
 | M9 | Installer | (meta) | none | all | P1 | 🟨 |
 | M12 | Session sharing (shared terminal) | Sharing | none (relay) | all | P3 | ✅ |
 | M13 | Auto-update | (core) | none (stdlib; user-local file swap) | all | P3 | ✅ |
+| M14 | AI assistant (explain diagnostics) | (optional) | none (stdlib urllib; Ollama or Claude) | all | P3 | ✅ |
 | ~~M7~~ | ~~Stress / repro~~ | — | — | — | — | ❌ dropped (D7) |
 
 ## Notes per module
@@ -117,6 +118,15 @@ Status: ⬜ not started · 🟦 designing · 🟨 in progress · ✅ done
   atomic symlink swap → restart, incl. the daemon). HTTPS-only, version-check-only (no
   telemetry), opt-out-able. Surfaced in the GUI; `rigdoctor update` in the CLI. (`.deb` users
   update via apt instead.)
+- **M14 AI assistant** (D24) — optional, **strictly opt-in, never automatic**: explains the
+  collected diagnostics in plain language only when the user presses **"Explain with AI"**
+  (`core/ai.py`, GUI button on the diagnostic dialog, `rigdoctor ai explain`). The user picks a
+  provider explicitly (no default): **Ollama** (local, private, no key) or **Claude** (Anthropic
+  Messages API, key in the keyring; consent prompt before sending). Answers are **grounded** —
+  we pass the actual findings plus matched reference facts from a curated knowledge base
+  (`core/ai_knowledge.py`, "RAG-lite": exact keyword/code match, no embeddings, stdlib only),
+  which lifts a small local model and sharpens Claude. Stdlib `urllib` (no pip deps); output is
+  advisory (D9). Configure in **Settings → AI assistant**.
 
 ## Bundles (final — D14)
 - **Essential:** M1 + M3 + M4  *(the MVP, NVIDIA-only — D5)*
@@ -124,6 +134,7 @@ Status: ⬜ not started · 🟦 designing · 🟨 in progress · ✅ done
 - **Diagnostics:** M5 + M6
 - **Desktop UI:** M10 + M11  *(adds PySide6)*
 - **Sharing:** M12  *(session sharing / remote assist — D16)*
+- **AI:** M14  *(optional AI explanations — D24)*
 
 ## MVP candidate — *confirmed (D5)*
 **M1 + M3 + M4 (Essential), NVIDIA-only, CLI-first.** Gives a working tool that captures the