v0.6.0

Added

• Compile-time diagnostics for configuration and imports. prima check now reports E0022
  for unknown config / with config keys (with a did you mean suggestion backed by the same
  key table the runtime uses), E0030 for imports that resolve to no module (embedded stdlib →
  hosted namespace → filesystem, matching the module loader), and E0032 for from-imports or
  qualified access to items that exist but are not pub. Dependencies are not recursively
  checked; the runtime keeps R0008 as the fallback for dynamic load failures.

• W0004 unreachable_code. Statements after a return in the same block are reported as a
  warning (spec §16.5).

• Diagnostics code-table guard. A test pins the appendix C code set and covers the four codes
  added in this release, so the document and the implementation cannot drift silently.

• mem::Arc explicit reference counting (spec §12.3/§12.4). import mem; now provides
  mem::Arc::new(x), a.clone(), a.get(), and a.strong_count(). The count starts at 1 and is
  raised only by an explicit clone; ordinary class-instance copies (let b = a) share the handle
  without changing it, and the count never decreases because the host layer has no destructor hooks.
  The four methods carry /// docs and appear in prima doc --stdlib.

• Pollard rho for math::factor. After stripping factors up to 10,000 by trial division,
  factor uses Miller–Rabin plus Brent's Pollard rho, so large semiprimes no longer require
  sqrt(n) divisions. Results stay ascending with multiplicity, and the bounded search falls back
  to trial division rather than returning a wrong answer.

Fixed

• ? now returns early from the enclosing Result/Option function. Previously ? on None
  raised R0011 and ? on Err raised a runtime error, so fn f() -> Option<T> { let x = xs.get(0)?; Some(x) } failed instead of returning None. The Err/None value is now carried
  by an internal propagation marker and caught at function-call boundaries, matching spec §16.3.

• prima check now agrees with the evaluator on valid symbolic code. Unbound single-segment
  identifiers in value position are free symbolic variables (as the evaluator already treated
  them), so prima check examples/ is clean except the intentionally broken example; only
  call-position names are undefined. Struct patterns with binding-only fields are irrefutable in
  let (no spurious E0053), and class or method names no longer produce W0003.