Release v20.61.3

Fixed

• A regex validation rule whose pattern already escapes a slash — Matches(@"^\d{2}\/\d{2}$") — generated a client validator that did not parse: the slash was escaped a second time, and the resulting \\/ let the slash terminate the regex literal early. Slash escaping is now escape-aware, so a pattern's own escapes pass through untouched and only a bare slash is escaped.
• An exact-length rule — Length(4) — projected to the client as length(0, 0), since the extractor read a Length property that ExactLengthValidator does not have. It reads the validator's Min (which carries the exact length) instead, so length(4, 4) is generated.

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Both were latent in the client validation projection introduced by #2363. The generation scenarios now hold the emitted proxy against the TypeScript compiler's own diagnostics rather than a best-effort transpilation — ts.transpile emits output even for code that does not parse, so the previous check could not fail — and a corpus scenario pins every projectable rule shape to its exact emission; it caught the exact-length defect on its first run. Both fixes verified to have teeth by reverting them and watching the specs fail. Full suite green: 3,987 passed, 0 failed.