fix(ci): drop private @taskade/eslint-plugin so the public repo installs everywhere

[johnxie]

Why CI is red on every branch (incl. master)

package.json listed @taskade/eslint-plugin (a private GitHub Packages package) in dependencies, and .eslintrc.json extended plugin:@taskade/base from it. So yarn install --frozen-lockfile returns 401 Unauthorized for anyone without taskade-org package access:

• every CI run is red — master, this branch, #19, all of them fail at the install step.
• no external contributor can install or build this public integration kit — a hard blocker for a repo whose whole point is community-portable integrations.

And the plugin was lint-only while CI only ran build+test (never lint) — so it was pure breakage for zero benefit.

Fix

Change	Effect
Remove @taskade/eslint-plugin from dependencies; regenerate yarn.lock	yarn install works for everyone — no private registry needed
Replace .eslintrc.json with a self-contained public config (eslint + @typescript-eslint)	linting is portable; lenient on the existing require()/any/@ts-ignore so it passes as-is
Add a lint script + a CI yarn lint step	now that lint is public and green, CI actually enforces it

Verified locally

yarn install · yarn lint · yarn build · yarn test (4/4) all green. This PR's own CI run will be the first green one in the repo.

Unblocks #19 and every future contributor.

🤖 Generated with Claude Code

[johnxie]

Folded into #19 so the task_due migration and the CI fix land together as one green, reviewable PR. The fix (drop the private @taskade/eslint-plugin, public eslint config, CI lint step) is unchanged — see #19.