GB-M0 — Audited agent skills and operating contract

[PNHD]

Purpose

Stage a minimal, audited repo-scoped agent-skill layer for GalaxyBridge without touching the active R1 writer branch.

Base / merge policy

Base: feature/gb-m0-feasibility
Head: chore/agent-skills-m0

DO NOT MERGE while an external Codex R1 session may still be writing to the base branch. Rebase/review after that writer finishes.

Added

• root AGENTS.md repository contract for Codex/agent work
• root CLAUDE.md with Claude-specific read-only/review defaults
• canonical docs/AGENT_HANDOFF.md
• docs/AGENT_SKILLS_AUDIT.md
• repo-scoped Codex skills under .agents/skills/
• matching Claude project skills under .claude/skills/

Installed skill scopes:

1. galaxybridge-ble-feasibility
2. galaxybridge-buds-protocol
3. galaxybridge-health-bridge

Audit choices

• Did not vendor dpearson2699/swift-ios-skills; its Core Bluetooth and HealthKit content was inspected and is useful as reference, but the repository uses PolyForm Perimeter 1.0.0 rather than a simple permissive license.
• Official android/skills is retained as a first-party reference; current catalog has useful Android CLI/testing/Wear UI material but no dedicated Bluetooth/RFCOMM skill found. Broad testing/UI skills are deferred to avoid M0 dependency/context bloat.
• Generic React Native/Flutter/mobile mega-skills are rejected for the native Swift/Kotlin architecture.
• No third-party skill auto-update policy; any future skill change must be re-audited.

Scope safety

No application source, protocol behavior or milestone status is changed by this PR.