refactor: delegate ol update to @doist/cli-core/commands (#68)

## Summary

Mirrors [twist-cli #214](Doist/twist-cli#214).
cli-core 0.9.0 owns the registry fetch, package-manager detection,
install spawn, channel switch, and `--json`/`--ndjson` envelopes.
outline provides the package name, version, config path, changelog hint,
and spinner runner.

PR 3 of a 3-PR stack — **stacked on #67**:
1. ✅ #66 — cli-core wiring (errors, config, spinner, output, markdown)
2. ✅ #67 — global-args + ViewOptions + empty-output test helper
3. **This PR** — delegate `ol update` to cli-core/commands

## Changes

- `src/commands/update/index.ts` now forwards to cli-core's
`registerUpdateCommand` with `{ packageName, currentVersion, configPath,
changelogCommandName: 'ol changelog', withSpinner }`.
- Delete `src/commands/update/action.ts` (203 lines) and
`src/commands/update/switch.ts` (37 lines) — cli-core owns both.
- Delete `src/lib/update-config.ts` (12 lines) — cli-core reads/writes
`update_channel` directly via the config path we hand it.
- `src/__tests__/update.test.ts` slims to a wrapper test (option
forwarding). ~400 lines of behaviour tests removed — covered upstream by
cli-core's update suite.
- `src/lib/skills/content.ts` documents the new `--json` flag on `ol
update --check`; `skills/outline-cli/SKILL.md` regenerated.

Net: **37 insertions / 710 deletions across 7 files.**

## Behaviour changes (mirroring twist-cli #214)

- Invalid `update_channel` on disk surfaces as `INVALID_UPDATE_CHANNEL`
from `ol update` (was silently coerced to stable).
- Errors emit canonical cli-core codes (`INVALID_FLAGS`,
`UPDATE_CHECK_FAILED`, `UPDATE_INSTALL_FAILED`).
- Both subcommands accept `--json` / `--ndjson` envelopes.

## Test plan

- [x] `npm run type-check`
- [x] `npm run lint:check` — 0 warnings, 0 errors
- [x] `npm test` — 103 tests pass
- [x] `npm run build && npm run sync:skill && npm run check:skill-sync`
— SKILL.md in sync
- [ ] Smoke `ol update --channel` — reports `stable`
- [ ] Smoke `ol update --check` — reports current vs latest with channel
line
- [ ] Smoke `ol update --check --json` — single-record JSON envelope
- [ ] Manual `ol update switch --pre-release` then `ol update switch
--stable` — flips on-disk `update_channel`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: scottlovegrove

skills/outline-cli/SKILL.md

@@ -82,6 +82,8 @@ ol auth logout                # Clear saved credentials
 ```bash
 ol update                        # Update CLI to latest version
 ol update --check                # Check for updates without installing, show channel
+ol update --check --json         # Check for updates as a JSON envelope
+ol update --check --ndjson       # Check for updates as NDJSON output
 ol update --channel              # Show current update channel
 ol update switch --stable        # Switch to stable release channel
 ol update switch --pre-release   # Switch to pre-release (next) channel

src/__tests__/update-surface.test.ts

@@ -0,0 +1,41 @@
+import { Command } from 'commander'
+import { describe, expect, it, vi } from 'vitest'
+import { registerUpdateCommand } from '../commands/update/index.js'
+
+// Stub out config + spinner — this test only cares about the command surface
+// (subcommand names + flags) wired up via the real cli-core, so a bump to
+// cli-core can't silently change `ol update`'s public CLI shape.
+vi.mock('../lib/config.js', () => ({
+    getConfigPath: () => '/tmp/outline-cli-test/config.json',
+}))
+
+vi.mock('../lib/spinner.js', () => ({
+    withSpinner: vi.fn((_opts: unknown, fn: () => Promise<unknown>) => fn()),
+}))
+
+describe('ol update command surface (integration with real cli-core)', () => {
+    it('exposes `update` with --check and --channel flags', () => {
+        const program = new Command()
+        registerUpdateCommand(program)
+
+        const update = program.commands.find((c) => c.name() === 'update')
+        expect(update).toBeDefined()
+
+        const longs = update?.options.map((o) => o.long) ?? []
+        expect(longs).toContain('--check')
+        expect(longs).toContain('--channel')
+    })
+
+    it('exposes `update switch` with --stable and --pre-release flags', () => {
+        const program = new Command()
+        registerUpdateCommand(program)
+
+        const update = program.commands.find((c) => c.name() === 'update')
+        const switchCmd = update?.commands.find((c) => c.name() === 'switch')
+        expect(switchCmd).toBeDefined()
+
+        const longs = switchCmd?.options.map((o) => o.long) ?? []
+        expect(longs).toContain('--stable')
+        expect(longs).toContain('--pre-release')
+    })
+})