feat(email): bind post content to Core blocks through one read-only binding source

[TheAggressive]

Replaces the snapshot-bound post blocks with real WordPress Core blocks connected to a single CampaignBridge Block Bindings source, without weakening the deterministic, immutable, snapshot-only compiler.

What changed

Removed	Replacement
campaignbridge/post-title	core/heading bound to title / titleLink
campaignbridge/post-excerpt	core/paragraph bound to excerpt / content
campaignbridge/post-button	core/buttons › core/button bound to url
campaignbridge/post-link	the same button with the native ghost style

Custom blocks drop from 12 to 8. campaignbridge/post-image stays: WordPress' get_block_bindings_supported_attributes() makes only id, url, title, alt and caption bindable on core/image, so link-to-post and the snapshot's intrinsic dimensions have no bindable path.

Binding contract

includes/Email_Blocks/email-blocks.json gains a postBindings section naming the one source — campaignbridge/post-data — and the only supported block + attribute + field + argument combinations. Both Core_Block_Normalizer and the editor read that file, so the editor cannot author a binding the compiler will not accept.

A field declares reads (the snapshot field supplying its value) and an optional link (the snapshot field the value links to). Bindings therefore resolve data; renderers own presentation. linkToPost survives as the titleLink field rather than a block attribute, and Heading_Renderer composes the anchor with the heading's own resolved colour, because email clients recolour bare links.

Read-only by construction

The source defines neither setValues nor canUserEditValue, so WordPress itself disables editing of every bound attribute and discards writes to it. It is deliberately not registered in PHP, so render_block() cannot substitute live post data either. Editing an email template can never modify the article it displays — asserted in a browser against real Gutenberg.

Compiler

Core_Block_Normalizer validates metadata.bindings against the contract and emits a canonical postBindings attribute; it never executes the source. Renderer_Interface::resolve_post_bindings() substitutes values from the Post Card's immutable snapshot after token resolution — so snapshot text can never be read as an authored provider token — and before validation, so a bound value passes the same rules an authored one does. No post is read during a compile.

Also included

• New optional content snapshot field exposing the post body as plain text, reduced without invoking the_content, shortcodes or dynamic blocks. Block boundaries are preserved as word boundaries: plain strip_tags would turn …epsilon</p><!-- wp:paragraph --><p>zeta… into one word.
• Bounded maxWords argument (10–500) shared by the excerpt and content fields.
• A contract-aware Post content inspector panel added through the public editor.BlockEdit filter. Core's own bindings panel reads one source-wide field list and cannot be scoped per attribute, so it would offer url on a paragraph.
• Colour diagnostics now name the attribute the author set instead of a generic color, so a theme palette slug with no email equivalent points at the control that produced it.
• Removes link-hover style support orphaned by the replaced blocks.

Compatibility

Templates saved with the four removed blocks no longer compile and must be rebuilt with the Core equivalents. No BREAKING CHANGE: footer was added, so semantic-release will not cut a major — say if you want that instead.

Verification

Command	Result
pnpm qa	OK — 1071 tests, 4777 assertions
pnpm qa:fast	OK — 122 JS tests, prettier, PHPStan clean
pnpm lint:php	clean
pnpm test:e2e	9 passed
pnpm build / release:package / release:verify	succeeded

One e2e run had native-editor and preview-personalization fail, then both passed in isolation and the full suite passed on re-run — parallel contention on a single local site, not a regression.

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