Drop HTML sample email templates from unpackaged/post

[jstvz]

What this does

Removes the two HTML sample email templates from unpackaged/post/email/Unsubscribe_Link/. Keeps the plain-text sample and fixes its merge field.

Why

The new package Unsubscribe-Link-4 delivers sample templates as unmanaged metadata through unpackaged/post, not inside the package. The two HTML samples cannot deploy this way.

The HTML samples call the packaged Visualforce component:

<c:UnsubscribeLink recipientId="{!recipient.Id}"></c:UnsubscribeLink>

When the sample lands in the subscriber default namespace (c) and the component stays in UnsubscribeLnk, the call crosses a namespace boundary. The platform then enforces a stricter rule: every attribute passed to a managed component from another namespace must be access="global". The recipientId attribute is not global, so the deploy fails:

Cannot use attribute recipientid (in component unsubscribelnk:unsubscribelink)
without global access in a component/page that is not in the same namespace
as the component

This is a consequence of the "deliver samples via unpackaged/post" model, not a template typo. It has been true since the component was first created (checked release/0.3.0.2); the package model just exposed it.

Changes

• Remove Unsubscribe_Contact_Template_HTML.email (+ meta).

• Remove Unsubscribe_Lead_Template_HTML.email (+ meta).

• Keep Unsubscribe_Lead_Template_Plain_Text.email. Add the CumulusCI namespace token so the merge field resolves in both managed and unmanaged contexts:

  {!Recipient.%%%NAMESPACE%%%Unsubscribe_Url_Plain_Text__c}
  

Verification

Built 1.0.0.1 of the new package and ran the same test the beta-test CI job runs after merge (ci_beta: install the managed package, deploy unpackaged/post, run Apex tests), pinned to 04tKf000000kjbHIAQ, in a fresh scratch org.

• Managed package install: PASS. No unfiled$public collision.
• Plain-text sample deploy: PASS.
• Apex tests: PASS.

HTML sample follow-up

HTML sample delivery is a product decision, tracked in a follow-up comment on #217. Two options: make the component attribute global and rebuild (a public-API commitment, new version), or ship the HTML sample as copy-paste documentation. This PR does not decide that. It only unblocks the install path.

[DKeatonDC]

These changes make sense and should proceed.