feat(ai): render Markdown + feed game/Proton/Steam logs to the AI — 0.28.0

1) The explanation popup rendered raw Markdown (### / **). Switched to
   QTextEdit.setMarkdown and told the model to answer in Markdown.
2) On "Explain with AI", also collect recent Proton (~/steam-*.log) and Steam
   console logs (core/gamelogs.py — tail-read, size-bounded) and include them in
   the prompt so the model can correlate log errors with findings and pinpoint
   when things went wrong. Reference-fact matching runs over the logs too.

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

src/rigdoctor/core/gamelogs.py

@@ -0,0 +1,67 @@
+"""Collect recent game / Proton / Steam logs to enrich an AI diagnostic (M14).
+
+Reads logs that already exist on disk — no change to how the game is launched. Two reliable
+sources: Proton's per-app log (``~/steam-<appid>.log``, written when ``PROTON_LOG=1``) and
+Steam's own console log. Each is tail-read and size-bounded so the AI prompt stays small. The
+text is fed to the AI alongside the findings so it can see *when* something went wrong (a
+vkd3d/DXVK error, a crash line, the exit code) rather than only the sensor summary.
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+# Steam keeps logs under its install root; ~/.steam/steam usually symlinks to the real one.
+_STEAM_LOG_DIRS = ("~/.steam/steam/logs", "~/.local/share/Steam/logs", "~/.steam/root/logs")
+_STEAM_LOG_FILES = ("console-linux.txt", "console_log.txt", "stderr.txt")
+
+
+def _tail(path: Path, max_bytes: int) -> str:
+    """Last ``max_bytes`` of a file, decoded leniently (empty string on error)."""
+    try:
+        size = path.stat().st_size
+        with path.open("rb") as fh:
+            if size > max_bytes:
+                fh.seek(size - max_bytes)
+            return fh.read().decode("utf-8", "replace")
+    except OSError:
+        return ""
+
+
+def _proton_logs() -> list[Path]:
+    try:
+        logs = list(Path.home().glob("steam-*.log"))
+    except OSError:
+        return []
+    return sorted(logs, key=lambda p: p.stat().st_mtime, reverse=True)
+
+
+def _steam_console() -> Path | None:
+    for directory in _STEAM_LOG_DIRS:
+        base = Path(os.path.expanduser(directory))
+        for name in _STEAM_LOG_FILES:
+            candidate = base / name
+            if candidate.exists():
+                return candidate
+    return None
+
+
+def available() -> bool:
+    return bool(_proton_logs() or _steam_console())
+
+
+def collect(max_bytes: int = 6000) -> str:
+    """Recent Proton + Steam log tails as one labelled text block ('' if none)."""
+    sections: list[str] = []
+    protons = _proton_logs()
+    if protons:
+        tail = _tail(protons[0], max_bytes).strip()
+        if tail:
+            sections.append(f"--- Proton log ({protons[0].name}) ---\n{tail}")
+    console = _steam_console()
+    if console:
+        tail = _tail(console, max_bytes).strip()
+        if tail:
+            sections.append(f"--- Steam log ({console.name}) ---\n{tail}")
+    return "\n\n".join(sections)