scheduling: scheduler durable object, /remind, automations

[anott03]

Summary

Adds a scheduling primitive for lynn, built in phases (design doc tracked locally in .thoughts/scheduler.md):

• Schedule spec module (src/schedule/spec.ts): one-shot, daily, and weekly schedule values with a branded default zone (America/New_York)
• Pure next-fire math (src/schedule/next-run.ts): strictly-after semantics, DST gap and overlap handling via Intl offsets
• Scheduler Durable Object (src/schedule/scheduler.ts): job registry backed by SQLite storage, alarm-driven firing, task dispatch by payload type, automation reconcile on boot
• Async command execution: Command.execute now returns Promise<CommandResult> end to end
• /remind command with at / every / list / cancel subcommands, plus mention-path parsing and a natural-language time parser (in 30 minutes, tomorrow 9am, monday 10am, 2026-09-01 14:30)
• Automation registry (src/discord/automations/index.ts): statically declared reminders reconciled into the DO on boot; ships an inert standup example until a channel id is configured

Verification

• tsc, oxlint clean; 41 vitest tests green (parser cases, DST fixtures, interaction handling)
• Live dev smoke: job fired on time through the alarm path, cancel/list behavior verified, adapter-to-DO chain exercised, reconcile skip/insert/delete all confirmed across boots
• Slash commands registered in the guild via pnpm register

Notes

• Recurring specs store wall-clock time plus IANA zone; UTC instants are computed only for next_fire_at so recurring jobs stay drift-free across DST transitions
• Cancel is permission-free; created_by is stored for display only
• The Gateway DO keeps its alarm reserved for reconnect logic, hence the dedicated Scheduler DO

Follow-ups

• Manual Discord QA of /ping, mention ping, and the four /remind flows on real channels
• Paste a real channel id into the standup example (or drop it) before enabling it
• Deploy to prod after review

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Preview Deployed

URL: https://lynn-lynn-pr-13-gej5zaoqllpq5oze.amitavnott.workers.dev

Built from commit 7a001c8

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