Retain closed initial policy closure failure diagnostics

[EHotwagner]

The retained Count1 attempt refused before browser startup and recorded only initial-closure:exception, leaving its inner cause unknown. Initial closure failures now retain a bounded, closed subcheckpoint and code, including unexpected exceptions; the capture parser and failure projection preserve that detail. Existing closure, custody and digest checks still fail closed, original exceptions are reraised, and noninitial diagnostic bytes are unchanged. Raw exception text and private material are never emitted.

Validation: locked Release build and the full runtime-evidence source gate pass, including genuine missing/hash/JSON/custody/argv controls, closed parser/projection and legacy-frame checks, 38 Quint scenarios, 500 invariant samples, complete-state/effect correspondence and 13 rejected mutants. Local verification used the official private SDK/Core and an explicit exact-commit SourceLink input because the local clone has no canonical remote metadata; canonical hosted qualification remains required.

The owning roadmap records this source evidence. The old native attempt remains refused with its exact cause unknown, useful play remains 0/6, and changed policy bytes require a protected successor build and a distinct future operation grant.