Visibility modifiers on class and record members are now enforced, not merely
parsed. A `private` member is reachable only within the declaring unit; a
`protected` member additionally within descendant types; `public`/`published`
everywhere the type is. Adds `strict private` and `strict protected`, which
narrow visibility to the declaring type itself (and, for strict protected, its
descendants) rather than the whole unit. `strict` composes with `static`.
Parser: track the current visibility section in class/record bodies and the
contextual `strict` keyword (only before private/protected); carry the
visibility onto each field, method, and property declaration. `strict public`,
`strict published`, and a bare `strict` are rejected.
Semantic: every qualified and unqualified member-access site checks visibility
via MemberVisibleTo / AssertMemberVisibleV, using the member's declaring unit
and declaring type. Static (class-level) vars now carry Visibility and
OwnerTypeName on their TSymbol so a qualified static-var access enforces the
same rules; a strict/private static var written from another type is rejected
with a "not accessible" diagnostic. Qualified static-var writes from a
permitted context are reported as not-yet-lowered rather than mis-resolved
(permitted writes use the unqualified form inside a static method).
Cross-unit: member visibility and declaring-type/unit origin are carried across
separately-compiled units in the .bif interface (BLAISE-IFACE version 5) so the
checks hold for imported types.
Updates docs/grammar.ebnf with the visibility-section grammar and adds
cp.test.visibility (parse + semantic enforcement) plus thread-test fixes that
switched two TThread subclasses from private FTerminated/FFinished fields to
the public Terminated/Finished properties.
a4190d73cf