Mantis #324 narrowly tightened fs.go from 0644/0755→0600/0700. Athena audit
during task #20 closure-verification (2026-04-25) found sibling files in the
same directory still using 0755 for MkdirAll, leaving parent dirs world-listable
even when file content is 0600.
This commit applies the same hardening to:
- .core/reference/error.go:393 — crash-report parent dir 0755→0700
- .core/reference/embed.go:514/567/656 — workspace template extract dirs 0755→0700
- .core/reference/embed.go:595/660 — os.Create→os.OpenFile(...0600) for
template renders + standard-file copies (default umask 0644 was leaking
workspace-template content to other users on shared hosts)
- pkg/lib/workspace/default/.core/reference/error.go:414 — same crash-report fix
- pkg/lib/workspace/default/.core/reference/embed.go:518/571/660 — same template fixes
Workspace-template duplicates are kept in sync so newly-scaffolded workspaces
inherit the hardened perms instead of regressing to 0755/0644.
Closes Mantis #988.
Co-authored-by: Codex <noreply@openai.com>
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