BR-2: sin agents-md embeds sin-brain inject block

[Delqhi]

Plan: docs/plans/bundle-memory-tools-integration.md (+ WS4 #4)

Idempotent AGENTS.md block between / , embedding sin-brain inject output + tool-usage + negative constraints (red-zones).

Acceptance:

• Re-running is idempotent (single managed block)
• Includes when-to-use-which-tool guidance
• Includes negative constraints section
  Depends on: SIN-Brain SB-4.

[Delqhi]

✅ COMPLETE — BR-2 implemented

sin agents-md now generates AGENTS.md with SIN-Brain Memory Protocol:

• recall before starting ANY task
• remember after completing
• pin for critical conventions
• 4-tier memory system explained
• Memory Rules section

Commit: 6d0c756
Tag: v0.3.3