When cwd is `~/.pi/agent/` or a subdirectory, the global AGENTS.md file
was included twice in the system prompt.
`loadProjectContextFiles()` loads context files in two steps:
1. Explicitly loads from `getAgentDir()` (`~/.pi/agent/`)
2. Walks from cwd up to root, collecting all AGENTS.md/CLAUDE.md files
There was no deduplication. When cwd is at or below `~/.pi/agent/`, the
ancestor walk includes that directory again.
Fix: track seen paths with a Set and skip duplicates.
a9a1a62b14