v0.2.0

anymodbus 0.2.0

Adds Modbus-ASCII framing, FC08 diagnostic loopback, FC04
input-register typed reads, and RS485 cold-start ergonomics — the
capabilities requested by servomexlib for its [modbus-ascii] / AUTO
milestone. The public API is additive and backwards-compatible; the internal
framing layer was restructured behind a narrow Framer strategy seam so
RTU / ASCII / (future) TCP share one response interpreter.

Added

• Modbus-ASCII framing — Bus(stream, framing=Framing.ASCII), the
  Framing enum, and an open_modbus_ascii(path, *, baudrate, parity, data_bits=8) opener (data_bits=7 for the classic 7E1 wire). Sync mirrors
  included.
• Pure LRC primitives at anymodbus.lrc: lrc8, lrc8_bytes,
  verify_lrc (mirroring anymodbus.crc).
• FC08 diagnostic loopback — Slave.diagnostic_loopback(data=b"\x00\x00")
  (FC 0x08 sub-0x0000, Return Query Data), a side-effect-free liveness probe.
• FC04 input registers in the typed reads — read_float / read_int32 /
  read_string accept source=RegisterSource.INPUT (default HOLDING).
• TimingConfig.startup_settle — one-shot pre-first-transaction settle for
  USB-RS485 adapter warm-up.
• ChecksumError base exception (parent of CRCError and new LRCError).
• MockSlave parity — answers FC08 sub-0 and speaks ASCII
  (MockSlave(framing=…), client_slave_pair(framing=…)).

Changed

• Default RetryPolicy.retry_on widened to {ChecksumError, FrameTimeoutError} so ASCII LRCError retries by default (RTU unchanged —
  CRCError ⊂ ChecksumError).
• FC 0x08 reclassified from known-unsupported to supported (sub-0 only).
  CRCError reparented under ChecksumError (still a ProtocolError).

No breaking changes to the documented public API. Full changelog in
CHANGELOG.md.