refactor: consolidate duplicate prompt files (prompts/chat/ vs autobot-backend/resources/prompts/chat/)

[mrveiss]

Problem

Two directories contain near-duplicate prompt files:

• prompts/chat/ (root)
• autobot-backend/resources/prompts/chat/ (backend resources)

Current drift between copies:

File	Diff lines
system_prompt.md	0 (identical — after manual fix)
installation_help.md	23
system_prompt_simple.md	94
api_documentation.md	21
architecture_explanation.md	21
troubleshooting.md	21

This duplication caused a bug this session: setup.sh refs were updated in the backend copy of system_prompt.md but missed in the root copy (caught in code review, fixed in ad0f24a).

Suggested Fix

Designate ONE canonical location and symlink or remove the other. The backend resources copy is likely authoritative (loaded by the backend at runtime).

Discovered During

Code review of #2420 — root system_prompt.md was missed because of duplication.

[mrveiss]

Merged in PR #2483.