[codex] Harden MEP route editing workflows

[epowell40]

Summary

• add guarded MEP branch/tap/network routing, explicit route editing, reroute-by-offset, and part-way size-transition workflows
• harden transition/takeoff fitting verification so unsupported cases block instead of leaving disconnected or wrong-fitting geometry
• improve focused visual capture for small MEP curve edits with crop metadata and trace overlays

Verification

• dotnet test apps/revit-bridge-addin/RevitBridge.Common.Tests/RevitBridge.Common.Tests.csproj --configuration Release --filter "MepRouteReroutePlannerTests" --no-restore
• dotnet build apps/revit-bridge-addin/RevitBridge.sln -c Release
• mirrored private/root verification also passed, including backend build, tool contract checks, skill manifest checks, Jest suite, and live Revit 2024/Snowdon GUI tests documented in the private EPIC

Notes

• Public core only: no hosted/deployment/customer/secret logic included.
• Live Revit proof covered duct tap/takeoff, pipe tee/tap guard, route edit, visual trace, reroute-by-offset, and isolated duct part-way size transition.