fix(mcp): update MCP configuration example to use array command format

[pablon]

Replace separate command/args fields with combined command array in mcp config directions when running engram --help

🔗 Linked Issue

Closes #88

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🏷️ PR Type

• type:bug — Bug fix
• type:feature — New feature
• type:docs — Documentation only
• type:refactor — Code refactoring (no behavior change)
• type:chore — Maintenance, dependencies, tooling
• type:breaking-change — Breaking change

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📝 Summary

• Updates MCP configuration example to use array command format

📂 Changes

File	Change
cmd/engram/main.go	Changes mcp json config for --help output

🧪 Test Plan

• Unit tests pass locally: go test ./...
• E2E tests pass locally: go test -tags e2e ./internal/server/...
• Manually tested the affected functionality

In opencode.json:

{
  "mcp": {
    "engram": {
      "type": "local",
      "command": ["engram", "mcp", "--tools=agent"],
      "enabled": true
    }
}

opencode mcp list command output:

┌  MCP Servers
│
●  ✓ engram connected
│      engram mcp --tools=agent
│
└  1 server(s)

opencode opens without errors ✅

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🤖 Automated Checks

These run automatically and all must pass before merge:

Check	What it verifies	Status
Check Issue Reference	PR body contains Closes #N / Fixes #N / Resolves #N	⏳
Check Issue Has status:approved	Linked issue has status:approved label	⏳
Check PR Has type:* Label	PR has exactly one type:* label	⏳
Unit Tests	go test ./... passes	⏳
E2E Tests	go test -tags e2e ./internal/server/... passes	⏳

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✅ Contributor Checklist

• I linked an approved issue above (Closes #N)
• I added exactly one type:* label to this PR
• I ran unit tests locally: go test ./...
• I ran e2e tests locally: go test -tags e2e ./internal/server/...
• Docs updated (if behavior changed)
• Commits follow conventional commits format
• No Co-Authored-By trailers in commits

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💬 Notes for Reviewers