Give repeated class evaluations fresh guest constructor identity

[nickna]

Implement the constructor-definition representation decided by #1906: each evaluation of a class expression creates a fresh guest constructor/definition object while sharing its pre-emitted CLR template. The consolidated #1866 PR will contain docs/plans/repeated-class-evaluation.md and tests/fixtures/RepeatedClassEvaluation/.

The original #1849–#1851 notes omit their exact repeated-evaluation source/deadline. New constructors-only.ts establishes the current mismatch on unchanged 0ad37b5 and 9a431d62: Node/CLI interpretation print false; IL-verified compiled standalone prints true, exit 0. Separate syntax-node tests from #1859 still pass; they do not repair evaluation identity.

Acceptance:

• Introduce fresh guest definition values per evaluation, retain declaration/template identity for checked compilation metadata, and associate constructed instances with the selected definition before field initialization.
• Route observable class value equality, new/Reflect construction and required direct constructor paths through the definition; preserve name/arity, prototype/constructor identity and definition-aware instanceof.
• Cover one syntax node evaluated twice in a function, loop, closure, module and suspended async/generator execution. Distinct definitions remain independent; CLR generic type arguments within one definition keep the same guest constructor/prototype.
• Match Node for constructors-only and prototype identity controls in both engines and verified standalone output under 30-second deadlines. Keep existing class expression/owner/local class/generic tests passing.
• Run affected constructor/generic/property tests, Release, quality gates and actual AOT analyzer baseline; report runtime, IL and hosted evidence separately.

Captured computed-key isolation is a separate dependent task. Stop at the definition identity/instance association boundary. Do not emit new CLR types at guest runtime, use a static "current definition", implement arbitrary dynamic heritage (#1907), or expand the frozen #1866 child list. This is a finite implementation transfer, not a claim of repaired behavior.