feat(scheduler): preset bundles for /onboarding + /schedule-add first-run (E15-B)

[kengio]

Summary

Three opinionated preset tiers (Minimal / Essentials / Maintenance Plus) + Custom escape hatch. Shown to users with empty schedule: block during /onboarding (default = Essentials) and /schedule-add Step 0. Idempotent + non-destructive — never re-prompts users with existing schedules.

• Plugin v2.4.8 → v2.4.9 · CLI unchanged at v2.3.1
• Tier 3 demonstrates skill + command modes coexisting (uses E15-A schema)
• Single source of truth at _shared/schedule-presets.md

Depends on

PR #173 (E15-A — hook-style command mode) merged to main. Tier 3 includes a command: onebrain entry that requires PR A's ScheduleEntry.command schema.

Preset tiers

# Tier 1: Minimal (1)
- cron: "0 9 * * *"
  skill: /daily

# Tier 2: Essentials Recommended (3)
- /daily 09:00 (every day)
- /weekly Friday 17:00 (workday-end)
- /recap Sunday 12:00 (weekend reflection)

# Tier 3: Maintenance Plus (6 — mixes skill + command modes)
- Essentials +
- /doctor 1st of month 09:00
- /tasks daily 06:00 (pre-work refresh)
- onebrain qmd-reindex Sunday 03:00 (command-mode, hook-style)

# Tier 4: Custom — drops to wizard

Workday vs weekend cadence

• All-day: /daily 09:00, /tasks 06:00
• Workday-end: /weekly Friday 17:00
• Weekend: /recap Sunday 12:00, onebrain qmd-reindex Sunday 03:00
• Calendar-pinned: /doctor 1st of month 09:00

Times staggered across the day (03/06/09/12/17) so launchd never spawns multiple OneBrain jobs simultaneously.

3-round review consensus

All 3 reviewers approved without required fixes:

• R1 (skill content) — single-source pattern holds; tier YAML in _shared/ only; idempotency contract clean
• R2 (docs + versioning) — placements correct; 5-bullet changelog within 8-cap; CLI unchanged at 2.3.1; memory rules pass
• R3 (spec compliance) — 10/10 acceptance criteria met; no src/ touched; English-only clean

Test plan

• /schedule-add with empty schedule: block prompts preset selector
• /schedule-add with non-empty schedule: block skips preset prompt (straight to wizard)
• Picking Tier 2 writes 3 entries and registers via onebrain register-schedule
• Picking Tier 3 writes 5 skill entries + 1 command entry (Tier 3 needs E15-A schema)
• /onboarding shows preset step with Essentials as default
• Skip in /onboarding writes no schedule entries
• _shared/schedule-presets.md is the only file containing tier YAML — no duplication

Out of scope

• Workday-only cron (Mon-Fri × 5 entries — too heavy for default)
• Customize-times-before-install flow (defer)
• Wizard support for constructing command-mode entries (defer; users hand-edit vault.yml)

Spec: `01-projects/onebrain/shared/2026-05-12-schedule-presets-design.md` (E15-B)
Plan: `01-projects/onebrain/shared/2026-05-12-schedule-presets-plan.md`
Depends on: #173 (E15-A scheduler command mode)