Orchestrate atomic development rebuilds before manager generation selection

[adrianwebb]

Objective

Make trsd dev rebuild execute the unprivileged local build, await an atomic completed overlay generation, apply declared consumer reactions, and only then mark the manager generation ready.

Reproduction

Session dev-f9dfe127-231: trsd dev rebuild ui.package currently only calls local.dev.rebuild, which increments state to pending. It neither runs/awaits the build nor waits for package-overlay synchronization. The overlay current link can select a marker-less partial generation, and Admin keeps the old realpath.

Requirements

• Run the target build locally with its declared timeout.
• For package targets, require a newly published overlay generation with the completion marker written last.
• Preserve the prior generation on failure.
• Apply dependency reactions after selection (reload, restart, rebuild, manual).
• Mark manager state ready only after the target and automatic consumers converge.
• Add delayed-marker and failure regression cases.