FSE: Front-end block context does not exist

[noahtallen]

Describe the bug
Note: This is caused by #22519. Before that commit, the issue does not occur.

In FSE blocks like post content or post title, the block context does not exist. For example, this statement is true, which returns early:

gutenberg/packages/block-library/src/post-content/index.php

Lines 17 to 19 in b83f948

	if ( ! isset( $block->context['postId'] ) ) {
	return '';
	}

I returned "what" there, and this is what the front end looks like:

(Above that line is also supposed to be a post title block.)

To reproduce
Steps to reproduce the behavior:

1. Turn on FSE
2. Visit a page on the front end
3. Page content does not display

Other settings:

1. Clean environment
2. Turned on FSE
3. demo templates remained off
4. Mapped a block theme
5. Changed customizer settings to show static front page

Expected behavior
Dynamic block content should display. (Currently seems related to block context.)

Screenshots
see above

Editor version (please complete the following information):
Latest pull in the local environment