fix(marketplace): switch plugin source to explicit HTTPS url form

[yotamleo]

Symptom

Installing this plugin's Claude Code marketplace entry on a fresh machine with no SSH key configured for github.com (no ~/.ssh/known_hosts entry, no key) fails with an SSH host-key verification error.

Impact

The plannotator-effective-html plugin entry in .claude-plugin/marketplace.json uses the github owner/repo shorthand source:

"source": {
  "source": "github",
  "repo": "plannotator/effective-html"
}

Claude Code resolves this shorthand by cloning over git@github.com:... (SSH). Any consumer without a pre-configured SSH key/known-hosts entry for GitHub — a fresh CI runner, a new dev machine, a sandboxed agent host — cannot install the plugin.

Repro

On a host with no ~/.ssh/known_hosts entry for github.com and no SSH key loaded, add this marketplace and run claude plugin install plannotator-effective-html@effective-html. The clone fails at SSH host-key verification.

Evidence

Upstream HEAD at the time of this PR: d95debbaef15af1d201fc6c10c77cf92b524a0d6, .claude-plugin/marketplace.json line 10-13.

Fix

Switch the source to the explicit HTTPS url form, which clones over HTTPS and needs no SSH setup:

"source": {
  "source": "url",
  "url": "https://github.com/plannotator/effective-html.git"
}

No other files reference the github-shorthand source (checked repo-wide); the .codex-plugin/plugin.json manifest is a separate, unrelated format with no such field.

[vercel]

Someone is attempting to deploy a commit to the Effective HTML Team on Vercel.

A member of the Team first needs to authorize it.

[ll88762543-dotcom]

It seems that the maintainer has not been online these days.