Local dev setup missing shows 706–988 — seed.sql outdated

The seed file (seed/seed.sql) only contains data up to show 705. On a fresh local setup, after running pnpm dev, only those shows are available until the admin import endpoint is manually triggered to sync the rest from the markdown files.

This creates a poor onboarding experience for new contributors — the site works but is missing ~280 episodes. It also makes it harder to investigate bugs affecting newer shows, for example syntaxfm/website#2170 (host names missing for shows featuring w3cj) was difficult to reproduce locally because those shows (742+) aren't in the seed data.

Two possible fixes:

1. Update seed.sql periodically to include newer shows — low-tech but requires manual upkeep
2. Auto-import from markdown on first run — preheat.js already has all the logic via import_or_update_all_changed_shows(), it could call that instead of (or after) seeding when the table is empty. Since all shows exist as .md files in the repo, no DB credentials or network access needed

Option 2 seems more maintainable long-term since the markdown files are always up to date in the repo.

Start with seed/seed.sql and preheat.js, especially import_or_update_all_changed_shows(), then inspect how pnpm dev initializes the local database and how the admin import endpoint is invoked. Decide how first-run initialization should load the markdown shows without network access, and verify that a fresh setup includes shows beyond 705, including those around 742.