v0.6.0

• Gen::string() / stringOf() / char() draw characters with a distribution
  that keeps strings readable and adversarial at once — half ASCII printable,
  a tenth from a list of troublemakers (quotes, backslash, <>&, tab and
  newlines, no-break space, soft hyphen, combining marks, zero-width space
  and joiner, right-to-left mark and override, line separator, byte order
  mark, replacement character, astral emoji, tag characters), a tenth
  Latin-1/Latin Extended, a tenth the rest of the Basic Multilingual Plane,
  a fifth uniform over U+0001..U+10FFFF — instead of uniformly over 1.1
  million codepoints, which met a quote once in a million characters and
  produced strings that were never ASCII. This changes the sequence a seed
  produces: FilesystemCorpus::SEQUENCE_EPOCH is now 2, and seed entries
  recorded by 0.5 and earlier are dropped from the corpus (values entries
  are unaffected).
• Gen::recursive() — and Gen::json() on top of it — shrink every level to
  its leaf first, so a nested value minimises to the plain value it wraps:
  [[[1]]] reaches 1, not merely []. Each level draws the leaf's seed at
  generation time (the sequence shifts, covered by the epoch above).
• Gen::datetime() generates with microsecond precision and shrinks toward
  the epoch through an integer ladder. Bounds keep their fraction
  (min = 12:00:00.5 no longer generates 12:00:00.0), and "any date after
  2000 fails" now minimises to the boundary instead of stopping at the
  original because the single epoch candidate passed.
• Gen::dictOf() with a string key generator redraws a canonical integer
  string ("12", "-3", "0"), which PHP would store under the integer
  key — the map stays the array<string, T> it declares.
• A corpus that throws (a Redis server refusing the connection, a client
  error) no longer escapes PropertyRunner::run(): the failure is a new
  CorpusFailed event (property id, operation, throwable) and the corpus is
  dropped for the rest of that run. The engine's promise that it never
  throws for a property outcome now covers the corpus.
• FilesystemCorpus takes one lock for the directory (.corpus.lock)
  instead of one .lock per property: a per-property lock file could never
  be removed safely and accumulated one file per property for good. A
  symlink at the lock path is refused, like the temp path.
• Both backends leave a document written by another format version as it
  is: it read as empty, and a write replaced it — the other version's memory
  lost without a trace. CorpusDocument::isForeignFormat() tells it apart
  from corrupt content, which is still replaced.
• The Redis clients address the compare-and-set script by EVALSHA
  (CorpusScript::SHA) and fall back to EVAL on NOSCRIPT: the script
  text travels once per server, not once per write.