Pi extension authoring

Ground every answer in pi-mono/ files below.

Grounding

pi-mono/packages/coding-agent/docs/extensions.md — capabilities, lifecycle, patterns.
pi-mono/packages/coding-agent/examples/extensions/README.md — runnable examples index.
pi-mono/packages/coding-agent/src/core/resource-loader.ts — extendResources() appends paths via mergePaths after existing lastSkillPaths (late paths lose name collisions to earlier ones unless names differ).
pi-mono/packages/coding-agent/src/core/agent-session.ts — extension commands vs queued prompts; skill expansion hooks.
pi-mono/packages/coding-agent/docs/tui.md — extension TUI component integration with @mariozechner/pi-tui: Component rendering contract, overlay patterns, input handling in extension context.
pi-mono/packages/coding-agent/docs/custom-provider.md — registerProvider() for proxies, OAuth/SSO, custom APIs, and custom model definitions.

Extensions can register tools, commands, themes, prompts, and extra skill paths; exact API surface is defined in docs and example modules — start from docs/extensions.md, not memory.
Dynamic resource discovery patterns live under pi-mono/packages/coding-agent/examples/extensions/ (e.g. dynamic-resources/ listing in examples README).