feat: add feature-map skill

[markphelps]

Adds feature-map to the development plugin. It builds a repo-local verification skill that tells agents what each user-facing feature is, how a user reaches it, how to drive it, what to observe, and the gotchas. It's based on Lauren Tan's (@poteto) feature-map idea.

How it works

• Two skills: feature-map is the builder, invoked manually as /feature-map, /feature-map refresh, or /feature-map <feature>. It writes verify-<app>/ into the repo's .claude/skills/ or .agents/skills/, and that generated skill triggers implicitly whenever an agent verifies a change. Its SKILL.md holds a feature index plus the verification loop; features/*.md load on demand.
• Verified by driving: features are discovered statically, then driven live. Only steps observed to work are recorded. Entries are marked verified: <sha> <date> or unverified: <reason>, and the index shows the verified ratio.
• Drivers: one reference each for web (role/label/test-id locators), CLI (real binary in a temp HOME), HTTP API, and macOS (accessibility tree, or XCUITest when present). Platforms can be mixed.
• Self-healing: the generated skill tells verifying agents to drive the entries whose paths overlap their diff, update only entries they drove based on what they observed, add entries for new features, and use nudge wording when an entry is missing.
• Findings: gaps that need code changes to become drivable (no stable selector, no accessibilityIdentifier) are listed, not fixed.
• Safety: local and dev environments only, ask before destructive or external actions, secrets only as env var names, and it never modifies source code.

whiteboard

Region templates gain an optional features: field. Feature entries can list regions:. Neither skill depends on the other.

Checks

Ran locally: npm run format:check, npm run validate, and npm run sync (mirror under skills/ included).