Release v3.1.0

v3.1.0 changes

BREAKING

• Library: Require destination port, transport, and canonical PLC profile when constructing connection options. Constructors remain local-only; commands require an explicit successful open and return HostLinkError::NotConnected instead of opening or reopening a transport.
• Library: Fix the communication timeout default at 3 seconds, normal command termination at CR, and the internal response-body cap at 65,536 bytes. Public LF and buffer-size controls are removed.
• Library: Make set_time require an explicit, calendar-valid HostLinkClock; local-time creation remains a separate caller-invoked helper and never falls back to UTC.
• Library: Change maintainer send_raw to return undecoded response-body bytes without converting PLC error responses. It is hidden from ordinary generated user documentation.
• Library: Remove comment padding options. Comment decoding removes only trailing ASCII space bytes before UTF-8/Shift_JIS decoding.
• Library: Require expansion-buffer and low-level numeric formats, reject suffix-bearing low-level device inputs, and validate response tokens, numeric ranges, counts, and 32-bit spans without fallback conversion.
• Library: Remove all public chunked helpers. Word and native Dword helpers send at most one request and reject counts over their one-request limit.
• Library: Keep bit-in-word read-modify-write under one client lock so concurrent clones cannot interleave the read and write portions.
• Library: Remove the embedded PLC manual error-message lookup and retain only the returned PLC code and response.
• Library: Require UDP response terminators, reject suffixes on every non-format command, validate hexadecimal reads as exactly one 1..4-digit token, and limit clock years to 00..99.
• Library: Validate command-derived response counts, including 16/32-point direct-bit numeric reads; accept only documented 0/1/ON/OFF direct-bit tokens and close the session after malformed semantic responses.
• Library: Replace the lossy From<HostLinkValue> for u16 conversion with fallible TryFrom, so non-U16 variants cannot silently become zero.
• Tests: Add explicit 3-second/zero/TCP-timeout recovery coverage and remove library-local cross-implementation vectors; cross-language verification is a separate repository concern.
• Tooling: Allow the local release gate to package the reviewed working-tree diff before it is committed.
• Samples: Require port, transport, and canonical PLC profile in every runnable endpoint definition.

Added

• Library: Added KvHostLinkPlcProfileDescriptor and crate-root plc_profile_descriptors() for canonical Host Link profile metadata.

Changed

• Docs: Rebuilt getting-started, usage, API, profile, README, examples, and maintainer migration material around the explicit quality-overhaul contract.

• Tests: Added coverage for disconnected commands, raw bytes, response caps and expected counts, native Dword requests, calendar validation, comment padding, and concurrent bit-in-word updates.

• Release: Bumped crate and lockfile metadata to 3.1.0.

Fixed

• Library: Corrected ten KV device range cells against live PLC hardware and the KEYENCE simulator, and pinned the canonical profile source to plc-comm-hostlink-profiles v1.2.0. VM widens to VM0-9999 on KV-NANO and VM0-59999 on KV-3000/KV-5000; Z widens to Z1-23 on KV-8000. CTH narrows to CTH0-1 on the KV-3000 and KV-5000 XYM profiles, matching their base profiles: CTH2 and CTH3 were previously accepted there and are now rejected.
• Library: Poison and replace TCP/UDP transports after timeout, I/O failure, or a dropped request future so delayed responses cannot satisfy a later request.
• Tests: Cover UDP timeout and cancellation with delayed loopback responses.
• Docs: Remove hand-maintained next-page navigation from Getting Started.

Release integrity

• The registry package, �3.1.0 tag, and attached assets remain immutable.
• Main-branch CHANGELOG classification was corrected by PR #27 without changing runtime code, package metadata, the tag, or published artifacts.