rename: system-prompt.md is the source of truth; agent identity = 'agency'

[MagMueller]

Summary

Stacked on #210 (simplify-v2). Two changes, one PR:

1. agent/CLAUDE.md → agent/system-prompt.md. Single source of truth. Both CLAUDE.md (Claude Code's filename) and AGENTS.md (Codex's filename) are symlinks pointing at it. Edit one file; both CLIs read the same content. On the box, install.sh installs system-prompt.md to /home/bux/system-prompt.md and symlinks both ~/CLAUDE.md and ~/AGENTS.md to it. bootstrap.sh re-asserts the symlinks on every update — boxes provisioned with the older "CLAUDE.md as a real file" layout self-heal.

2. Agent identity renamed bux → agency. The product/box/repo is still bux (Browser Use Box). The agent voice is agency. Splits the brand from the persona.

Plus:

• New top-of-file "How the whole system works" section (5 bullets, one screen). Anything else is detail.
• Visual-first emphasis in "How you talk" — generate images (PIL, screenshot, matplotlib) when an image helps faster than text. Phone users especially.

Test plan

• 29 unit tests pass
• Shell syntax check for install.sh + bootstrap.sh
• Symlink layout verified: agent/CLAUDE.md and agent/AGENTS.md → system-prompt.md; root AGENTS.md → agent/system-prompt.md
• First-install on a fresh box — verify Claude Code reads ~/CLAUDE.md through the symlink chain
• Update on an existing box (CLAUDE.md was a real file) — verify bootstrap converts it to the symlink layout

🤖 Generated with Claude Code

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Summary by cubic

Make agent/system-prompt.md the single source of truth for the agent prompt and rename the agent voice to "agency". Both ~/CLAUDE.md (Claude Code) and ~/AGENTS.md (Codex) now symlink to /home/bux/system-prompt.md.

• Refactors

  • Renamed agent/CLAUDE.md → agent/system-prompt.md; repo AGENTS.md now points to it.
  • Updated install.sh and bootstrap.sh to install /home/bux/system-prompt.md and re-assert symlinks; self-heals old boxes that had a real ~/CLAUDE.md.
  • Agent identity: bux → agency (product/box/repo stays "bux").
  • Added a concise "How the whole system works" section and a visual-first note in "How you talk".

• Migration

  • No manual steps. On update, a real ~/CLAUDE.md is replaced by a symlink.
  • If you script against the prompt, use /home/bux/system-prompt.md.

^{Written for commit b1af8e7. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

No issues found across 7 files

_{Re-trigger cubic}