chore: install openagent opencode

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

.opencode/context/core/context-system/operations/update.md

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+<!-- Context: core/update | Priority: medium | Version: 1.0 | Updated: 2026-02-15 -->
+
+# Update Operation
+
+**Purpose**: Update context when APIs, frameworks, or contracts change
+
+**Last Updated**: 2026-01-06
+
+---
+
+## When to Use
+
+- Framework version updates (Next.js 14 → 15)
+- API changes (breaking changes, deprecations)
+- New features added to existing topics
+- Migration guides needed
+
+---
+
+## 8-Stage Workflow
+
+### Stage 1: Identify Changes (APPROVAL REQUIRED)
+**Action**: User describes what changed
+
+**Format**:
+```
+What changed in {topic}?
+  [A] API changes
+  [B] Deprecations
+  [C] New features
+  [D] Breaking changes
+  [E] Other (describe)
+
+Select all that apply (A B C D or describe):
+```
+
+**Follow-up**: Get specific details for each selected type
+
+**Validation**: MUST get user input before proceeding
+
+---
+
+### Stage 2: Find Affected Files
+**Action**: Search for files referencing the topic
+
+**Process**:
+1. Grep for topic references across all context
+2. Count references per file
+3. Show impact analysis
+
+**Format**:
+```
+Found 5 files referencing {topic}:
+  📄 concepts/routing.md (3 references, 145 lines)
+  📄 examples/app-router-example.md (7 references, 78 lines)
+  📄 guides/setting-up-nextjs.md (2 references, 132 lines)
+  📄 errors/nextjs-errors.md (1 reference, 98 lines)
+  📄 lookup/nextjs-commands.md (4 references, 54 lines)
+
+Total impact: 17 references across 5 files
+```
+
+---
+
+### Stage 3: Preview Changes (APPROVAL REQUIRED)
+**Action**: Show line-by-line diff for each file
+
+**Format**:
+```
+Proposed updates:
+
+━━━ concepts/routing.md ━━━
+
+Line 15:
+  - App router is optional (use pages/ or app/)
+  + App router is now default in Next.js 15 (pages/ still supported)
+
+Line 42:
+  + ## Metadata API (New in v15)
+  + Next.js 15 introduces new metadata API...
+
+━━━ examples/app-router-example.md ━━━
+
+Line 8:
+  - // Optional: use app router
+  + // Default in Next.js 15+
+
+Preview next file? (yes/no/show-all)
+Approve changes? (yes/no/edit):
+```
+
+**Edit mode**: Line-by-line approval for each change
+
+**Validation**: MUST get approval before proceeding
+
+---
+
+### Stage 4: Backup
+**Action**: Create backup before updating
+
+**Location**: `.tmp/backup/update-{topic}-{timestamp}/`
+
+**Purpose**: Enable rollback if updates cause issues
+
+---
+
+### Stage 5: Update Files
+**Action**: Apply approved changes
+
+**Process**:
+1. Update concepts, examples, guides, lookups
+2. Maintain MVI format (<200 lines)
+3. Update "Last Updated" dates
+4. Preserve file structure
+
+**Enforcement**: `@critical_rules.mvi_strict`
+
+---
+
+### Stage 6: Add Migration Notes
+**Action**: Add migration guide to errors/
+
+**Format**:
+```markdown
+## Migration: {Old Version} → {New Version}
+
+**Breaking Changes**:
+- Change 1
+- Change 2
+
+**Migration Steps**:
+1. Step 1
+2. Step 2
+
+**Reference**: [Link to changelog]
+```
+
+**Location**: `{category}/errors/{topic}-errors.md`
+
+---
+
+### Stage 7: Validate
+**Action**: Check all references and links
+
+**Checks**:
+- All internal references still work
+- No broken links
+- All files still <200 lines
+- MVI format maintained
+
+---
+
+### Stage 8: Report
+**Action**: Show comprehensive results
+
+**Format**:
+```
+✅ Updated X files
+📝 Modified Y references
+🔄 Added migration notes to errors/
+💾 Backup: .tmp/backup/update-{topic}-{timestamp}/
+
+Summary of changes:
+  - concepts/routing.md: 2 updates (145 → 162 lines)
+  - examples/app-router-example.md: 4 updates (78 → 89 lines)
+  - guides/setting-up-nextjs.md: 1 update (132 → 133 lines)
+
+All files still under 200 line limit ✓
+
+Rollback available if needed.
+```
+
+---
+
+## Change Types
+
+### API Changes
+- Method signatures changed
+- Parameters added/removed
+- Return types changed
+
+### Deprecations
+- Features marked deprecated
+- Replacement APIs available
+- Timeline for removal
+
+### New Features
+- New capabilities added
+- New APIs introduced
+- New patterns available
+
+### Breaking Changes
+- Incompatible changes
+- Migration required
+- Old code won't work
+
+---
+
+## Examples
+
+### Framework Update
+```bash
+/context update for Next.js 15
+/context update for React 19
+```
+
+### API Changes
+```bash
+/context update for Stripe API v2024
+/context update for OpenAI API breaking changes
+```
+
+### Library Update
+```bash
+/context update for Tailwind CSS v4
+```
+
+---
+
+## Success Criteria
+
+- [ ] User described changes?
+- [ ] All affected files found?
+- [ ] Diff preview shown?
+- [ ] User approved changes?
+- [ ] Backup created?
+- [ ] Migration notes added?
+- [ ] All references validated?
+- [ ] All files still <200 lines?
+
+---
+
+## Related
+
+- guides/workflows.md - Interactive diff examples
+- standards/mvi.md - Maintain MVI format
+- operations/error.md - Adding migration notes