refactor: aggressive scope pruning to essentials

Prune security infrastructure to a 2-layer exfiltration defense model:
firewall (primary) + narrowed hook (trusted channels only). Remove
permission tiers, most hooks, all commands, niche agents, and supporting
docs. Local destruction is no longer blocked -- devcontainer is disposable.

Deleted: 4 hooks, 3 commands, 6 agents, 1 skill, 3 tier files, 7 docs
Kept: 2 hooks, 6 agents, 4 skills, 4 rules, 1 plugin
Updated: settings.json, devcontainer.json, CLAUDE.md, DECISIONS.md,
DEVELOPMENT_PROCESS.md, IMPLEMENTATION_PLAN.md, all test files

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: stranma