Release v4.156.0

Changed

• Every MCP proposal result now carries a short human summary, also returned as a second text block after the JSON: which documents change, which modules, features, slices, commands, events, read models, screens and reactions are added or removed, what the authoring checks reported, how many comments are dropped and whether the result is executable. (#711)
• Proposal results explain their authoringDiagnosticCount: the new authoringDiagnosticSeverities splits it into errors, warnings and information with the distinct codes, and a note says it counts checks run while proposing, including the PLAY0288 canonical-printing notice, while after.readiness counts diagnostics of the resulting source alone. (#711)