feat(#126): display showcase posts in fortnightly showcase-digest - #134

You should run the linter and formatter as well, to fix some smaller issues.
We have a pre-commit in the repo, make sure it is properly installed, maybe it didn't run when you committed.

I can also suggest to use AI for a simple code-review beforehand, it is good at pattern finding and would find some issues, like the misspelled emoji, the shortend variable names and such, since it is described in the agents file. On claude you can do /code-review low, here is an output example on your branch:

src/features/showcase-digest/config.ts:6 — Number.parseInt never throws, so the try/catch is dead. A non-numeric SHOWCASE_DIGEST_LOOKBACK_DAYS (e.g. abc) yields NaN, and filterPostsByCreationTime then never matches, so every run reports "no valid posts".
src/features/showcase-digest/config.ts:6 — the fallback warning is logged even when a value was set but failed to parse, so the log misreports the configuration.
src/common/commands/index.ts:14 — the new createDigestCommand is registered as digest-force in triggers.ts, but the import comes from triggers.js, which also starts the cron scheduler at import time. Worth confirming that importing this module from the command map does not start the scheduler twice alongside initializeShowcaseDigestScheduler() in ready.
src/features/showcase/create-showcase.ts:88 — an unrelated blank line was removed. This is cosmetic drift outside the feature and should be dropped from the diff.