test(s7): live python-snap7 coverage for the #632/#638 codecs, TSAP override and PDU size (#632)

Extends the s7_1500 profile (DB1 2048 bytes, 'hex' seed type) with distinct
non-zero seeds for STRING/WSTRING/CHAR/WCHAR/DTL/DATE/TOD/TIME/S5TIME plus
undecodable buffers; S7_1500CodecTests covers reads, BadOutOfRange paths,
write round-trips (S7_SIM_ALLOW_WRITES=1), TSAP keys and negotiated PDU size.
Skips when S7_SIM_ENDPOINT is unreachable.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

docs/drivers/S7-Test-Fixture.md

@@ -49,6 +49,13 @@ The driver ctor change that made this possible:
 - `S7_1500SmokeTests.Driver_write_then_read_round_trip_on_scratch_word` —
   `DB1.DBW100` write → read-back; proves write path + buffer visibility
 
+- `S7_1500CodecTests` (#632/#638) — live python-snap7 coverage of the STRING / WSTRING / CHAR / WCHAR /
+  DTL / DATE / TOD / TIME / S5TIME codecs: seeded reads (DB1 800..960, distinct non-zero), BadOutOfRange
+  reads of undecodable buffers, write round-trips and BadOutOfRange refused writes (scratch DB1 1100..1199;
+  needs `S7_SIM_ALLOW_WRITES=1`), the `LocalTsap`/`RemoteTsap`/`ConnectionType` override keys (proves they
+  reach the wire; snap7 accepts any TSAP, so TSAP semantics remain hardware-only), and the negotiated PDU
+  size (`NegotiatedPduSize` / `GetDiagnostics`). Seed map in `Docker/README.md`.
+
 ### Unit
 
 - `S7AddressParserTests` — S7 address syntax (`DB1.DBD0`, `M10.3`, `IW4`, etc.)