feat: add agentic concepts explainer to docs site

[justinjdev]

Summary

• New /concepts page on the documentation site explaining agentic workflows and agent orchestration for beginners
• Seven sections: agentic workflows, structure, orchestration, isolation, context engineering, human-in-the-loop, CTA
• Each section has a "In Fellowship" callout card connecting the general concept to how fellowship implements it
• Added "Concepts" nav link after "Getting Started"
• Writing targets people who've never heard of agent orchestration — no jargon, concrete examples

Test plan

• Verify site builds cleanly (cd site && npm ci && npm run build)
• Check page renders correctly at /concepts in both light and dark themes
• Verify nav link appears and highlights correctly
• Verify responsive layout on mobile (callout cards, CTA links stack)
• Check all internal links (/getting-started, /how-it-works) resolve

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added a "Concepts" section to the navigation menu
  • New "Agentic Workflows & Orchestration" documentation page covering workflow structure, orchestration, parallel execution, context engineering, and human-in-the-loop patterns

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 3dea1532-6cb8-4471-8a05-dbd1f40c7f4f

📥 Commits

Reviewing files that changed from the base of the PR and between 0e8acc8 and 8dc2b61.

📒 Files selected for processing (2)

• site/src/lib/components/Nav.svelte
• site/src/routes/concepts/+page.svelte

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📝 Walkthrough

Walkthrough

A navigation link to a new "Concepts" page is added to the navigation component, and a new concepts page is created covering agentic workflows and orchestration with structured content sections, internal CTAs, responsive styling, and in-page navigation anchors.

Changes

Cohort / File(s)	Summary
Navigation Enhancement site/src/lib/components/Nav.svelte	Added a new navigation entry linking to the concepts page with standard active-state and mobile menu behavior.
New Concepts Page site/src/routes/concepts/+page.svelte	Created new page with article content covering agentic workflows, orchestration, isolation & parallel execution, context engineering, and human-in-the-loop patterns. Includes internal CTAs, fellowship callout cards per section, and responsive styling.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/concepts-page

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