Replace ## Heading sections with descriptive XML tags (<role>, <task>,
<execution_protocol>, <examples>, etc.) for unambiguous first-order vs
second-order delimiter separation per Anthropic best practices.
- shared.ts: All constants wrapped in their XML tag
- Mode prompts: Consistent tag vocabulary and ordering across all 5 modes
- Examples use <examples> > <example label="good/bad"> nesting
- workspace.ts: Output wrapped in <workspace> tags
- Delete dead src/agent/prompts.ts (zero imports)
- Update docs/agent.md with XML tag documentation