feat(standard): rename §3.3 Priority 3 to "Secure / Security By Design" — v1.25

[UnbreakableMJ]

Summary

• Renames §3.3 Priority 3 from Hardened Security → Secure / Security By Design
• Aligns the priority name with the Security By Design principle (security built in from the start rather than bolted on)
• Body content of §3.3 (kernel hardening, sandboxing, PQC readiness, dependency auditing) is unchanged
• Bumps standard to v1.25 / 2026-06-20

Test plan

• grep "Hardened Security" The_Steelbore_Standard.md → 0 hits (excluding changelog prose)
• grep "Secure / Security By Design" The_Steelbore_Standard.md → hit at §3.3 heading
• Version is 1.25 and date is 2026-06-20 in frontmatter and masthead

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