refactor(cli): use incur natively (single root, built-in skills + mcp)

[douglance]

What

Replaces the hand-rolled CLI scaffolding — a custom root dispatcher, a command registry, two separate Cli builders (start-cli.ts / local-cli.ts), custom --help/--version formatting, and a custom skills merger — with a single idiomatic incur root Cli.

All commands now mount on one root:

Cli.create("testnode", { description, version, sync, mcp })
  .command(startCli).command(initCli)…
  .serve();

So skills add, mcp add, --help, --version, and --llms all come built in from incur — no bespoke wiring.

Why it was tangled

Every "local" command (init, logs, snapshot, status, stop, clean) resolved the project root at module-load time (const PROJECT_ROOT = findProjectRoot()), which throws when run outside the repo. That single import-time side effect is the only reason the commands couldn't share one root — importing them eagerly would crash testnode start. So everything got split + lazily import()ed behind a custom dispatcher.

The fix: make project-root resolution lazy (resolved inside run() via a memoized projectRoot()), so all commands can be eagerly registered on one root.

Changes

• Delete commands/registry.ts, start-cli.ts, local-cli.ts, commands/skills.ts.
• Rewrite index.ts to the single-root incur pattern with sync (skills) + mcp options.
• Lazy projectRoot() in project-root.ts; the 6 local commands resolve paths in run() (no behavior/output change).
• Version now read from package.json (was hardcoded "0.1.0" → now 0.2.5).
• Net −107 lines.

Supersedes #18

Skills now come from incur's built-in skills add (the sync option), so this replaces the custom skills.ts from #18. Closing #18 in favor of this.

Verification

• pnpm validate / pnpm test:run green (161 tests, incl. updated skills.test.ts).
• testnode --help lists all commands + skills add / mcp add.
• testnode skills add → syncs 7 skills; testnode mcp add → registers MCP server.
• testnode snapshot --help → subcommands preserved.
• Key invariant: testnode start --help from a non-repo dir does not throw a project-root error (lazy resolution; eager-importing @arbitrum/testnode-core is import-safe).
• No behavior/output changes to existing commands.