docs: finish rename sweep — no more 'pysniff' shorthand

Follow-up to ad3ff6b: the two remaining prose mentions of the old
short name become SIMtrace Analyser (AGENTS.md v1.9.0 note, test
comment).  Upstream 'simtrace2-sniff'/'simtrace2' references stay --
those are the Osmocom tool/hardware, not the renamed project.

AGENTS.md

@@ -348,7 +348,7 @@ RST line events (sub_type 0x10) now append the measured CLK frequency when
 it is known: `[direction, level, flags, clk_hz_be32]`, with `flags` bit 0
 (`LINE_EVENT_FLAG_CLK_HZ`) set and the frequency as a big-endian uint32 in
 Hz (7-byte payload).  An unknown rate keeps the 3-byte payload, so
-consumers that read only the first two bytes (e.g. pysniff's
+consumers that read only the first two bytes (e.g. SIMtrace Analyser's
 `decode_line_event`) are unaffected.  The value is the existing 16-edge
 average (`samplerate / _samples_per_clock`, see `_measure_clock_period`);
 PPS changes F/D, not the CLK rate, so one measurement per session is

tests/test_gsmtap.py

@@ -606,8 +606,8 @@ class TestLineEventPayload(unittest.TestCase):
         self.assertEqual(len(self.pd.line_event_payload(1, 0, 0)), 3)
 
     def test_legacy_prefix_preserved(self):
-        # Consumers that read only bytes 0-1 (pysniff decode_line_event)
-        # must see the same direction/level as before.
+        # Consumers that read only bytes 0-1 (SIMtrace Analyser's
+        # decode_line_event) must see the same direction/level as before.
         p = self.pd.line_event_payload(1, 0, 3579000)
         self.assertEqual(p[:2], b'\x01\x00')