fix(schema): support value-type API response results

[iriswolf]

Summary

• refresh the generated Telegram response envelope with generator contract version 12;
• allow value-type results such as bool without invalid System.Text.Json metadata;
• preserve legitimate false results during serialization;
• prepare aligned package hotfix 1.0.0-alpha.14.1.

Root cause

TelegramApiResponse<TResult>.Result used JsonIgnoreCondition.WhenWritingNull. With an unconstrained generic, TResult? is still a non-nullable value type for TResult = bool, so System.Text.Json rejected the generated contract before serialization or deserialization.

WhenWritingDefault is intentionally not used because Telegram may return a legitimate false result which must remain in the envelope.

Touched public surface

• generated TelegramApiResponse<TResult> JSON metadata only;
• no client request path, routing path, transport retry path, or handler dispatch path changed.

Verification

• generator ./eng/verify.ps1: 7 passed
• TeleFlow ./eng/verify-release.ps1 -PackageVersion 1.0.0-alpha.14.1 -Configuration Release: 868 passed
• strict analyzers: 0 warnings, 0 errors
• package output and metadata verification passed
• schema guardrails: 793 generated files checked
• formatting, whitespace, and git diff --check passed

Dependency

Generated from TelegramSchemaGenerator main after IWFTech/TelegramSchemaGenerator#24 was merged.