docs (flashblocks): add overview page and improve structure

[roethke]

What changed? Why?
Improves Flashblocks documentation based on the Deep Dive blog post, which was proving more helpful for teams than the existing docs.

Updates:

• New Overview page — Architecture, transaction lifecycle, block building algorithm, and integration guidance
• Better formatting, tables, and cross-references
• Improved Flashblocks section readability
• Updated docs.json — Added overview to navigation

Notes to reviewers

How has it been tested?
Locally

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[ericbrown99]

This is incorrect unless something has changed.

If a transaction consumes 20Mgas, it can be included as early as the 2nd flashblock (so long as the first flashblock has at least 1.25M gas unconsumed.

[ericbrown99]

There is a max gas limit per transaction. now, but this is different than the size of an individual flashblock

[ericbrown99]

How could we use mintlify components to improve the organization of this page? Would drop downs or toggles be better so that people can view only the answers they want to?

Approved review 3712473321 from ericbrown99 is now dismissed due to new commit. Re-request for approval.