Module lookup

[AnastaZIuk]

This PR fixes a critical runtime-module loading issue and hardens package consumption.

What was wrong

• Build and install interfaces were mixed during runtime lookup.
• A consumer executable could load DLLs from the wrong tree.
• In the worst case this loaded host-build binaries instead of packaged binaries.
• That could lead to config/ABI mismatch, missing symbols, startup failure, or runtime crash on consumer machines.

What is fixed

• Runtime lookup mode is now selected by runtime layout.
• Executables started from build tree resolve modules from build outputs.
• Executables started from installed package resolve modules from package-relative paths.
• The env-based runtime switch was removed from this path.
• Consumer-side package integration avoids exposing absolute-path compile definitions.

What was added

• Helper API for runtime module setup with build-time or configure-time copy and optional install rules.
• Smoke CI coverage for MINIMALISTIC, CONFIGURE_ONLY, and BUILD_ONLY.
• Updated consumption docs with concrete usage flows.

Out of scope in this PR

• Nabla build-interface targets still compile with some absolute-path defines.
• This is a known legacy post Irrlicht build-system limitation.
• Fixing it requires a larger build-system refactor and is intentionally outside this PR scope.