[codex] Harden PackageNormalize ZIP handling

[Widthdom]

Summary

• Harden PackageNormalize ZIP entry attribute handling by rejecting unsafe POSIX/DOS metadata and scrubbing destination external attributes.
• Bound and sanitize PackageNormalize failure diagnostics, cap package arguments, and report cleanup deletion failures as per-package JSON warnings.
• Document the normalizer safety and diagnostics contracts in both English and Japanese sections.

Validation

• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~ReleaseWorkflowTests -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj -c Release --filter FullyQualifiedName~ReleaseWorkflowTests -p:UseSharedCompilation=false
• dotnet run --project tools/CodeIndex.Changelog -- check
• dotnet build CodeIndex.sln -p:UseSharedCompilation=false
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll status --check --json

Documentation and Changelog

• Updated DEVELOPER_GUIDE.md in English and Japanese.
• Added changelog.d/unreleased/3552.fixed.md.
• Added changelog.d/unreleased/3458.fixed.md.

Adversarial Review

No blocking/actionable issues found.

Follow-up Candidates

None.

Fixes #3552
Fixes #3458