refactor: delegate ol changelog to @doist/cli-core/commands

[scottlovegrove]

Summary

• Changelog command — src/commands/changelog.ts is now a thin wrapper over registerChangelogCommand from @doist/cli-core/commands, passing path, repoUrl, version, and bulletMarkers: ['*', '-'] (preserves outline's local support for both bullet styles). Drops ~110 lines of local parsing/formatting now owned by cli-core.
• Top-level error handler — src/index.ts now matches instanceof BaseCliError so errors thrown from cli-core helpers (e.g. the delegated changelog command's INVALID_TYPE / FILE_READ_ERROR) route through formatError / formatErrorJson. The local CliError extends the same base, so existing throws still match.
• Global JSON flag — declared --json and --ndjson at the program level with enablePositionalOptions(), plus an isJsonMode() helper in src/lib/global-args.ts backed by cli-core's parseGlobalArgs argv scan. ol --json <subcommand> now produces a JSON error envelope for any BaseCliError thrown after parsing.
• formatError / formatErrorJson — widened in src/lib/output.ts to accept either positional (code, message, hints?) or a BaseCliError instance.
• src/lib/errors.ts — re-exports CoreCliError as BaseCliError so the top-level instanceof check covers both.

Mirrors todoist-cli#319. No @doist/cli-core version bump (already on 0.9.0).

Behavior changes

• ol changelog -n abc now exits non-zero with Error: INVALID_TYPE / Count must be a positive integer (was a custom chalk.red('Error:') line with Count must be a positive number) — intentional alignment with the cli-core contract.
• ol --json changelog -n abc now emits {"error":{"code":"INVALID_TYPE","message":"Count must be a positive integer"}}.
• --json / --ndjson now appear as global options in ol --help (existing per-subcommand --json flags still work the same).

Test plan

• npm run type-check
• npm run lint:check + npm run format:check
• npm test (108 tests pass; changelog suite slimmed from 6 tests to 2 wrapper smoke tests covering path-passthrough and footer URL; output suite gains BaseCliError-instance + formatErrorJson cases)
• Smoke ol changelog -n 1 — version block + footer link unchanged
• Smoke ol changelog -n abc — human red error, exit 1
• Smoke ol --json changelog -n abc — JSON error envelope, exit 1
• Smoke ol doc list --json — per-subcommand --json still routes to output formatter

🤖 Generated with Claude Code

[doistbot]

This PR cleanly delegates the changelog command to @doist/cli-core and introduces helpful top-level error handling for JSON output. These updates significantly streamline the codebase by reusing core utilities and establishing a more consistent error-reporting contract. A few adjustments are noted regarding the impact of positional options on existing global flags, ensuring consistent JSON flag behavior across successful commands, and refining the test suite and agent skill documentation to fully capture the new functionality.

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