fix(mcp): replace stale Context7 config entries

[LCubero]

🔗 Linked Issue

Closes #57

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🏷️ PR Type

What kind of change does this PR introduce?

• type:bug — Bug fix (non-breaking change that fixes an issue)
• type:feature — New feature (non-breaking change that adds functionality)
• type:docs — Documentation only
• type:refactor — Code refactoring (no functional changes)
• type:chore — Build, CI, or tooling changes
• type:breaking-change — Breaking change (fix or feature that changes existing behavior)

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📝 Summary

• Replaces managed Context7 MCP entries atomically so stale local fields cannot survive deep merges.
• Fixes OpenCode/KiloCode upgrade paths where legacy mcp.context7 fields like command, args, or env break strict schema validation.
• Adds regression coverage for idempotent migration and sibling MCP entry preservation.

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📂 Changes

File / Area	What Changed
internal/components/mcp/context7.go	Wraps managed Context7 overlay entries in __replace__, including OpenCode/KiloCode strict-schema config.
internal/components/mcp/inject_test.go	Adds structured regression tests for OpenCode/KiloCode stale field replacement, idempotency, and managed Context7 entries.

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🧪 Test Plan

Unit Tests

go test ./internal/components/mcp ./internal/components/filemerge ./internal/components/engram
go test ./...

E2E Tests

cd e2e && ./docker-test.sh

• Unit tests pass (go test ./...)
• E2E tests pass (cd e2e && ./docker-test.sh)
• Manually tested locally

Additional local verification used Fedora Podman as a Docker-compatible shim:

docker(){ podman "$@"; }; export -f docker; cd e2e && ./docker-test.sh

Result: Ubuntu, Arch, and Fedora E2E platforms passed (PASSED 3/3).

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🤖 Automated Checks

The following checks run automatically on this PR:

Check	Status	Description
Check Issue Reference	⏳	PR body must contain Closes/Fixes/Resolves #N
Check Issue Has status:approved	⏳	Linked issue must have been approved before work began
Check PR Has type:* Label	⏳	Exactly one type:* label must be applied
Unit Tests	⏳	go test ./... must pass
E2E Tests	⏳	cd e2e && ./docker-test.sh must pass

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✅ Contributor Checklist

• PR is linked to an issue with status:approved
• Maintainer needs to add the type:bug label
• Unit tests pass (go test ./...)
• E2E tests pass (cd e2e && ./docker-test.sh)
• I have updated documentation if necessary
• My commits follow Conventional Commits format
• My commits do not include Co-Authored-By trailers

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💬 Notes for Reviewers

This keeps the existing deep-merge behavior globally and uses the repository's existing __replace__ sentinel only for managed Context7 server entries. That preserves unrelated user MCP entries while preventing stale fields from contaminating OpenCode/KiloCode's strict mcp.context7 schema.

Because this PR is opened from a fork, I cannot add labels to the upstream PR. Maintainer action needed: please add type:bug.

[LCubero]

Reopened after local revision. Keeping this as draft while waiting for a maintainer to add the required type:bug label.