v3.15.0 — Framework alignment: Security + Cadence + BC-001/BC-002

Framework release v3.15.0. See aget-framework/aget v3.15.0 for full release notes.

Breaking changes in this release:

• BC-001: version.json old field names removed
• BC-002: --fix flag removed from skill surfaces; use /aget-enhance-health instead

New in this release:

• /aget-enhance-health skill (SKILL-049 v1.0.0)
• AGET_SECURITY_SPEC v0.2 + AGET_BUDGET_GRAMMAR_SPEC v0.2
• POL-REL-001 weekly Saturday release policy