docs(agent-guides): adopt progressive disclosure

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Summary

• reduce the root AGENTS.md to project-wide essentials and conditional documentation pointers
• split testing/CI, Git and stacked PRs, CherryUI composition, device isolation, naming, code organization, and runtime ownership into focused guides and references
• replace the Expo template README, align the repository on root pnpm@11.8.0, and register gh-stack plus vercel-composition-patterns

Validation

• pnpm docs:check-links
• pnpm skills:check
• pnpm lint (passes with existing warnings)
• pnpm format:check
• pnpm typecheck
• git diff --check upstream/v0.2...HEAD
• local Conductor lifecycle tests: 5 passing node --test cases plus a real prepare/status/cleanup cycle with no simulator, metadata, or allocated-port residue

The full local pnpm test was intentionally not run. The complete suite remains the remote CI gate after this draft is marked ready.

Follow-ups

• move any behavior protected by ModelSettingsScreen.test.tsx to lower-level tests, then remove the screen render suite
• handle existing non-kebab-case package filenames as a dedicated migration rather than incidental churn

The Conductor simulator and port lifecycle automation is machine-local under .conductor/settings.local.toml and is not part of this repository diff.

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Superseded by #542 so the bottom PR uses an in-repository branch and can be included in the GitHub Stack. The replacement contains the same commits and description.