Analysis of TIA Portal V19 pcap captures (xBiggs, GH-710) revealed the
root cause of the ConnectionReset after SessionKey auth:

TIA Portal's post-SetupSession sequence:
  1. SET_VARIABLE (0x04F2) — write attribute 323 on session
  2. GET_VAR_SUBSTREAMED — read from InObj=50, addr 7920 (finalize)
  3. Data reads work immediately (no password needed)
  4. Legitimation (addr 303/1846) happens later, optionally

Our code was skipping steps 1-2 and jumping straight to legitimation
(read challenge → write blob → finalize), which caused the PLC to
return V254 SYSTEM_EVENT error 0xE9 and RST subsequent requests.

Changes:
- Add _session_activate() that mirrors TIA Portal's activation:
  SET_VARIABLE attr 323 + GET_VAR_SUBSTREAMED InObj=50 addr 7920
- Only call _post_auth_legitimation() when a password is provided
  (previously ran unconditionally, even with empty password)
- Reorder: activate first, then legitimation (if password given)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Replace duplicate _skip_typed_value (73 lines) with codec.skip_typed_value
  import; fixes DWORD bug (was VLQ instead of fixed 4 bytes)
- Initialize _session_auth_public_key/_session_auth_family in __init__
  instead of using hasattr() guards
- Remove redundant lazy imports (DataType, LegitimationId already at
  top level)
- Make SessionKey and TLS auth mutually exclusive in client.connect()

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Data2Collection table 1 had 2111 entries (4222 bytes) but its 33
operations require 2112 entries (4224 bytes). The missing final word
0x4C28 caused IndexError during session key renewal when a challenge
selected the last lookup block.

Backported from HarpoS7 commit 22b9dc0 (bonk-dev/HarpoS7#24).

Adds:
- The missing 0x4C28 entry in fp_data2.bin
- Lookup table size invariant test
- Regression test with captured renewal challenge 5B15B469...

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Move _parse_create_object_response (120 lines, connection.py) into
  codec.py as parse_create_object_attributes — a reusable function that
  returns ServerSessionVersion, public key fingerprint, and session
  challenge in a CreateObjectAttributes dataclass. Both sync connection
  and async_client can use it.
- Keep parse_server_session_version as a thin wrapper for backward compat.
- Fix: add session_auth/**/*.bin to pyproject.toml package-data so
  binary data files (fp_data, transform12 metadata) ship in wheels.

Net: -69 lines.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>