NX Loom 0.27.0 — progress, cancel, and the end of the freeze

You asked for a progress bar and a cancel button; the freeze report made it three features.

• Progress bar. Slow rebuilds and Suggest Arcs now run in the background in small slices — the UI stays alive, and the sidebar shows a live bar ("filling patch 34/80", "tracing flow 3/12") with the status bar and cursor tracking the percentage.
• Cancel button. Right next to the bar. Cancelling is always safe: results are only written at the very end, so a cancelled job leaves your mesh, layout and ghosts exactly as they were.
• The freeze watchdog. Auto-cancel After (Size panel, default 60 s, 0 = off) bounds every calculation, including Apply's capture. A runaway solve gets cancelled cleanly instead of freezing Blender, and the panel tells you the mesh is stale and why. The solver's "a nudge can never un-solve your layout" guarantee is explicitly clock-independent.

Under test: the chunked build is bit-identical to the old blocking one; cancel and timeout at any point leave the document untouched. Suite: 423 headless + 16 GUI checks, 122-layout sweep clean.