fix(ai): analyse the actual session, not stale/benign logs — 0.28.1

The user ran a game ~20s with no crash but the AI dredged up old log lines,
guessed the wrong game, and gave Windows advice. Fixes:
- Prompt now includes the real game name + capture duration + outcome (clean vs
  crash), so the model uses the known game instead of guessing from log paths.
- gamelogs.collect(since=…): scope Steam-console lines by timestamp and skip a
  stale per-app Proton log (mtime before the session) — no unrelated past run.
- ai_knowledge: flag benign Steam/Proton lines (libnvidia-ml.so.1 assertion,
  routine minidumps, "fork without exec") as non-causal.
- System prompt: Linux-only steps (no "run as administrator"); don't manufacture
  a problem on a clean run.

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

tests/test_gamelogs.py

@@ -1,6 +1,8 @@
 """Tests for M14 game/Proton/Steam log collection."""
 
+import os
 import tempfile
+import time
 import unittest
 from pathlib import Path
 from unittest import mock
@@ -45,5 +47,31 @@ class CollectTests(unittest.TestCase):
             self.assertEqual(gamelogs.collect(), "")
 
 
+class SinceScopingTests(unittest.TestCase):
+    def test_since_filter_keeps_window_only(self):
+        text = (
+            "[2026-05-22 13:00:00] old session line\n"
+            "[2026-05-22 13:00:01] another old line\n"
+            "[2026-05-22 14:30:00] new session launch\n"
+            "[2026-05-22 14:30:05] new session error\n"
+        )
+        since = time.mktime(time.strptime("2026-05-22 14:00:00", "%Y-%m-%d %H:%M:%S"))
+        out = gamelogs._since_filter(text, since)
+        self.assertIn("new session launch", out)
+        self.assertIn("new session error", out)
+        self.assertNotIn("old session", out)
+
+    def test_collect_skips_stale_proton_log(self):
+        tmp = Path(tempfile.mkdtemp())
+        proton = tmp / "steam-9999.log"
+        proton.write_text("stale proton output from an earlier game")
+        old_mtime = time.time() - 3600
+        os.utime(proton, (old_mtime, old_mtime))
+        since = time.time() - 60  # session started a minute ago
+        with mock.patch.object(gamelogs, "_proton_logs", return_value=[proton]), \
+             mock.patch.object(gamelogs, "_steam_console", return_value=None):
+            self.assertEqual(gamelogs.collect(since=since), "")  # stale log excluded
+
+
 if __name__ == "__main__":
     unittest.main()