[AnthonyRonning]

Windows setup currently hides the failing native check behind a generic “could not be completed safely” message. The existing error dialog now includes the failure stage, full Windows/WinTrust error code, and short guidance for known failures. This also prepares the requested Agent 0.0.15 update.

Preflight/preparation retain full native error bits and fixed nonzero validation categories. The standalone historical-signature probe supplies the same error types to the shared verifier as the normal library build. Existing bootstrap arguments, activation status encoding, rollback, ACL, signature, publisher and timestamp checks remain unchanged. Existing real install/reinstall, launch/icon and uninstall smokes are unchanged. Version edits affect only the Agent workspace and its eight local lockfile entries; external dependencies are unchanged.

Refs #1369. The customer's Windows 10 failure remains undiagnosed. This improves the next report; it does not establish that the customer can install successfully or qualify Windows 10.

Validation:

• 84 updater library tests, 85 Windows packaging tests, 9 Git-metadata tests, locked version metadata, Rust formatting, whitespace and the repository lane's six macOS root flake checks passed locally before the rebase; the final contract-test assertion also passed all 85 packaging tests.
• Windows packaging/install rehearsal at pre-rebase commit 761a23f1: 40938570851 passed build/package and all existing installation smokes. Later revisions add master’s Settings/update UI change, strengthen one contract assertion, and fix the shared verifier’s standalone example import context; the installer logic is unchanged. The rebased PR head has its own required native compilation/updater checks. Unsigned evidence is not signed release evidence.
• Two experimental GUI-observer runs (40931125509, 40934815125) timed out without reading the new error dialog. Their logs are preserved. That newly introduced harness is excluded from this patch; no preexisting smoke or native safety check is removed. The new error dialog has not been visually verified.
• Broad local just ci was stopped during dependency rebuilding to keep this improvement bounded; local commit hooks were skipped for the handoff. These are not claimed as passed. Required PR CI 40940152589 passed on final head 525d4c83: all seven selected lanes and ci-ok, including 100 native Windows updater library tests and 5 integration tests with zero failed or ignored. No manual CI dispatch will be made on the open PR branch.

No publication, infrastructure, signing-environment, credential, root-certificate or security-policy changes. Release publication follows an approved merge and the normal signed-artifact checks and approvals.