chore: install openagent opencode

Signed-off-by: Dmytro Stanchiev <git@dmytros.dev>

.opencode/context/core/context-system/standards/mvi.md

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+<!-- Context: core/mvi | Priority: critical | Version: 1.0 | Updated: 2026-02-15 -->
+
+# MVI Principle (Minimal Viable Information)
+
+**Purpose**: Extract only core concepts, not verbose explanations
+
+**Last Updated**: 2026-01-06
+
+---
+
+## Core Idea
+
+Extract the **minimum information** needed for an AI agent to understand and use a concept:
+- Core concept (1-3 sentences)
+- Key points (3-5 bullets)
+- Minimal working example
+- Reference link to full docs
+
+**Goal**: Scannable in <30 seconds. Reference full docs, don't duplicate them.
+
+---
+
+## The Formula
+
+```
+Core Concept (1-3 sentences)
+  ↓
+Key Points (3-5 bullets)
+  ↓
+Quick Example (5-10 lines)
+  ↓
+Reference Link (full docs)
+  ↓
+Related Files (cross-refs)
+```
+
+---
+
+## What to Extract ✅
+
+- **Core definitions** - What it is (1-3 sentences)
+- **Key properties** - Essential characteristics (3-5 bullets)
+- **Minimal example** - Simplest working code (5-10 lines)
+- **Common patterns** - How it's typically used (2-3 bullets)
+- **Critical gotchas** - Must-know issues (1-2 bullets)
+- **Reference links** - Where to learn more
+
+---
+
+## What to Skip ❌
+
+- **Verbose explanations** - Link to docs instead
+- **Complete API docs** - Summarize + reference
+- **Implementation details** - Show minimal example + reference
+- **Historical context** - Unless critical to understanding
+- **Marketing content** - Just the facts
+- **Duplicate information** - Say it once, reference elsewhere
+
+---
+
+## Example: JWT Authentication
+
+### ❌ Too Verbose (400+ lines)
+```markdown
+# JWT Authentication
+
+JSON Web Tokens (JWT) are an open standard (RFC 7519) that defines 
+a compact and self-contained way for securely transmitting information 
+between parties as a JSON object. This information can be verified and 
+trusted because it is digitally signed. JWTs can be signed using a 
+secret (with the HMAC algorithm) or a public/private key pair using RSA 
+or ECDSA.
+
+[... 400 more lines of explanation, examples, edge cases ...]
+```
+
+### ✅ MVI Compliant (~50 lines)
+```markdown
+# Concept: JWT Authentication
+
+**Core Idea**: Stateless authentication using JSON Web Tokens signed 
+with a secret key. Token contains user data (payload) that server can 
+trust because signature is verified.
+
+**Key Points**:
+- Token has 3 parts: header.payload.signature (Base64 encoded)
+- Server verifies signature to trust payload without database lookup
+- No session storage needed (stateless)
+- Tokens expire (include `exp` claim)
+- Store in httpOnly cookie or Authorization header
+
+**Quick Example**:
+```js
+// Sign token
+const token = jwt.sign(
+  { userId: 123, role: 'admin' }, 
+  SECRET_KEY, 
+  { expiresIn: '1h' }
+)
+
+// Verify token
+const decoded = jwt.verify(token, SECRET_KEY)
+console.log(decoded.userId) // 123
+```
+
+**Reference**: https://jwt.io/introduction
+
+**Related**: 
+- examples/jwt-auth-example.md
+- guides/implementing-jwt.md
+- errors/auth-errors.md
+```
+
+---
+
+## File Size Limits
+
+<rule id="size_limits" enforcement="strict">
+  - Concept files: max 100 lines
+  - Example files: max 80 lines
+  - Guide files: max 150 lines
+  - Lookup files: max 100 lines
+  - Error files: max 150 lines
+  - README files: max 100 lines
+</rule>
+
+**Why**: Forces brevity. If you need more, split into multiple files or reference external docs.
+
+---
+
+## Validation Checklist
+
+Before creating a context file, verify:
+
+- [ ] Core concept is 1-3 sentences?
+- [ ] Key points are 3-5 bullets?
+- [ ] Example is <10 lines of code?
+- [ ] Reference link is included?
+- [ ] File is <200 lines total?
+- [ ] Can be scanned in <30 seconds?
+
+If any answer is "no", apply more compression.
+
+---
+
+## Related
+
+- structure.md - Where files go
+- compact.md - How to minimize
+- templates.md - Standard formats
+- creation.md - File creation rules