docs: add Fluent system architecture guide

[hedwig0x]

Summary

Add a new architecture doc for Fluent at a mid-technical level, focused on system design rather than code internals.

• New page: docs/knowledge-base/system-architecture.md
• Covers architecture from node shell -> execution coordination -> runtime layer
• Explains blended execution model, routing model, interruption protocol, syscall layering, gas/fuel model, and upgrade/security boundaries

Source alignment

This draft was built from:

• fluentlabs-xyz/tech-book architecture chapters (blended execution vision, EE model, interruption concepts)
• current fluentbase/docs/* runtime docs (00-08) for implementation-accurate behavior and terminology

When historical tech-book phrasing and current runtime docs differ, this page follows current Fluentbase runtime docs.

Validation

• npm ci
• npm run build (Docusaurus build succeeds)

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Project	Deployment	Actions	Updated (UTC)
docs-docusaurus	Ready	Preview, Comment	Apr 3, 2026 7:16pm

[hedwig0x]

Update based on review feedback:

• replaced the single compact page with a nested System Architecture section under Knowledge Base
• expanded content into 9 focused pages to better match tech-book scope while staying implementation-aligned with current Fluentbase docs
• emphasized architecture boundaries and integration challenges (routing/ownership, interruption/syscalls, state model, gas/fuel, upgrades/security)
• re-ran docs build after restructuring (npm run build passes)

New section path:

• docs/knowledge-base/system-architecture/

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[hedwig0x]

Moved System Architecture from nested to a top-level docs category () so it appears at the upper sidebar level. Build re-checked after move.

[hedwig0x]

Correction: System Architecture now lives at top-level path docs/system-architecture/ (not under Knowledge Base), so it shows in the upper sidebar level as requested.

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