refactor: agent config helper, integration helpers split, and tool cleanup

[awdemos]

What this PR does

A bundle of internal refactors that reduce duplication and tighten the public surface area:

1. mcpserver: collapse wrapTool and wrapToolWithClient into one wrapper.
2. mcpserver: remove single-field single-tenant setters that were only used by tests.
3. environment: share service startup and tunneling logic between RunBackground and startService.
4. integration tests: split helpers.go into setup.go, actions.go, and direct.go, then remove the stale monolith.
5. agent config: centralize config-file error wrapping in writeMcpConfig and use it across all agent configs (Claude, Codex, Cursor, Goose, Q).
6. environment: introduce FileEditRequest to reduce FileEdit parameter count.
7. environment: split FileRead into FileRead and FileReadRange.

Order / dependencies

This PR must be merged after the three feature PRs in this series:

1. mcpserver: add MCP roots support for better repo-open error messages
2. repository: inherit project-level git config and never run user hooks
3. mcpserver: add environment_log and environment_diff tools

The refactor branch is based on upstream/main plus those three changes, so once they land this PR will show only the refactor commits.

[awdemos]

This is a useful refactor, but it needs conflict resolution before it can land.

What it does well:

• Extracts a shared writeMcpConfig helper across agent configurations.
• Introduces FileEditRequest to reduce FileEdit's parameter count.
• Splits FileRead into FileRead and FileReadRange.
• Splits the integration test helpers into smaller, focused files.
• Tests pass locally: go test -short ./... passes.

Blocker:

• GitHub reports the PR as conflicting with main. The merge-tree output shows conflicts in cmd/container-use/agent/configure.go, configure_claude.go, configure_codex.go, etc. These overlap with other recently opened/merged agent config changes.

Recommendation: rebase onto upstream/main, resolve the agent-config conflicts, and push the updated branch.

[awdemos]

I rebased this PR onto upstream/main and resolved the agent-config conflicts. The branch is now clean and mergeable — ok github.com/dagger/container-use/cmd/container-use (cached)
ok github.com/dagger/container-use/cmd/container-use/agent (cached)
ok github.com/dagger/container-use/environment (cached)
ok github.com/dagger/container-use/environment/integration (cached)
ok github.com/dagger/container-use/mcpserver (cached)
ok github.com/dagger/container-use/repository (cached)
? github.com/dagger/container-use/rules [no test files] passes. No further action needed from the author unless they want to review the rebased history.