[Epic] Institutionalize Architectural Pre-Flight Skills

Description

This Epic formally tracks the graduation and implementation of the paired architectural pre-flight skills, established via consensus in Discussions #11252 and #11253. These skills formalize mutation-time governance by ensuring all architectural placements and memory-substrate mutations undergo structural validation before execution.

The two-sibling artifact structure prevents architectural fatigue by separating agent-loaded memory mutations from broader cross-substrate architectural decisions.

Sibling Artifacts

1. /turn-memory-pre-flight (from #11252)

   • Purpose: A dedicated pre-flight gate guarding turn-loaded or skill-loaded memory substrate (AGENTS.md, AGENTS_ATLAS, .agents/skills/**).
   • Risk Axis: Future-session mutation risk. Prevents improper substrate placement from biasing future sessions before a task-specific skill is chosen.
   • Discoverability: 1-line trigger in AGENTS.md §21.

2. /architecture-pre-flight (from #11253)

   • Purpose: An umbrella router for high-level architectural decisions (new daemons, subsystems, cross-substrate refactors).
   • Trigger Rule: Fires ONLY when no narrower mandatory trigger applies OR when work spans multiple trigger families.
   • Bypass Rule: Routine cases (e.g., new .mjs → /structural-pre-flight, new skill → /create-skill) bypass this umbrella to avoid substrate fatigue.

Acceptance Criteria

• Create .agents/skills/turn-memory-pre-flight/SKILL.md with explicit decision-tree logic for substrate placement.
• Create .agents/skills/architecture-pre-flight/SKILL.md as the high-level router-of-uncertainty.
• Update AGENTS.md §21 to include a 1-line trigger for /turn-memory-pre-flight targeting memory substrate modifications.
• Update AGENTS.md §21 to include a 1-line trigger for /architecture-pre-flight targeting broad, cross-substrate architectural ambiguity.
• Explicitly subsume and close #10837 as a Progressive Disclosure subcase within /turn-memory-pre-flight.
• Cross-link #10757 (cognitive-load epic) without fully absorbing it.
• Validate successful deployment of skills via testing and peer review (cross-family review mandate).