Scans colon-separated OLLIE_SKILLS_PATH (default ~/.config/ollie/skills)
for directories containing SKILL.md with name/description front-matter.
Reads from disk on every call, no caching. Deduplicates by name.
Move the system prompt from an inline Go string to prompts/SYSTEM_PROMPT.md,
loaded at runtime from ~/.config/ollie/prompts/ via text/template. The prompt
is now editable without recompilation and focuses on behavioral guidance
rather than token-saving directives.
- Remove systemPromptBase constant and token-efficiency instructions
- Add DefaultPromptsDir() for prompt directory discovery
- Load and render SYSTEM_PROMPT.md with {{.WorkDir}}, {{.Platform}}, etc.
- Update mkfile to install prompts/ to ~/.config/ollie/prompts/