Tighten solver trace validation

[xtraid]

Summary

• bind SAT solutions exactly to the referenced region bounds, active map, boundary, and tileset
• require each recorded decision to match its following decision reduction
• preserve initial-propagation changes across search backtracks
• reject every out-of-range event cell before kind-specific replay
• enforce status-dependent solution digests in the standalone validator
• mirror replay and bundle checks in the isolated renderer

Regression coverage

• hash-consistent tile-table recoloring
• active-map, boundary, and coordinate drift
• false decision candidates
• backtracks below the initial-change floor
• indexing and non-indexing out-of-range event cells
• SAT/null and UNSAT/non-null solution digests

Validation

• make check: 146 Python tests, 17 C test binaries, Pages checks, native and cross-engine smoke
• renderer: 258 passed
• make coverage-python: completed successfully (informational, no threshold)
• git diff --check

The native solvers, schemas, dependencies, fixtures, generated assets, and workflows are unchanged.