[100 MRG] Feature: responsive preview HTML sidecar

[TUPM96]

100 MRG

Emit preview HTML alongside XML for local browser check.

Acceptance

• Screenshots in PR

Claim (MergeOS MRG)

1. Follow https://github.com/mergeos-bounties
2. Star https://github.com/mergeos-bounties/mergeos
3. Star https://github.com/mergeos-bounties/mergeos-contracts
4. Comment on this issue: I claim this bounty
5. Comment on MergeOS Claim Token #1 with this issue link
6. Open a PR to BloggerEasy default branch with Fixes #<n>

Payout

Maintainer review → merge → MRG credit 25 / 50 / 100 / 200 only.

[jfust3]

I claim this bounty

[samuelpatak-png]

I claim this bounty

[laurentketterle-hub]

/attempt #78

PR: #155

[laurentketterle-hub]

I claim this bounty — @laurentketterle-hub ready to implement.