Wire topology preview and layout wizard

[daredoole]

Stacked on #12. This continues the roadmap work without changing the default beta runtime path.

What changed:

• Adds the line-based topology model/parser and validation for machines, displays, explicit links, wrap policy, and edge transition resolution.
• Wires topology into runtime as an opt-in dry-run preview via topology_enabled/topology_file; invalid or missing topology falls back to current behavior.
• Adds a desktop topology/layout wizard for side-by-side, stacked, AAB, BAA, ABA, and manual/asymmetric layouts.
• Documents the topology file contract and validates every documented example in CTest.

Local verification:

• cmake -S . -B build
• cmake --build build -j2
• ctest --test-dir build --output-on-failure
• scripts/validate-rpm-packaging.sh
• bash -n mwb-desktop-ui.sh
• bash -n scripts/inputflow-diagnostics-bundle.sh
• python3 tests/topology_config_docs_test.py docs/topology.md
• git diff --check

Note: topology handoff remains resolver/trace-gated. This PR intentionally logs dry-run transitions and preserves existing input injection behavior until direct cross-machine handoff enforcement is ready.

[daredoole]

Manual CI passed for roadmap/runtime-topology-layout-wizard: https://github.com/daredoole/inputflow-linux/actions/runs/25084868627

Jobs passed: Static checks, Fedora build and tests, Ubuntu build and tests, ASan/UBSan.

[daredoole]

Updated PR #13 with direct topology handoff enforcement in 2c3b2a7. Manual CI passed: https://github.com/daredoole/inputflow-linux/actions/runs/25085184197

Jobs passed: Static checks, Fedora build and tests, Ubuntu build and tests, ASan/UBSan.

[daredoole]

Updated PR #13 with user-readable topology setup in 138e490. Manual CI passed: https://github.com/daredoole/inputflow-linux/actions/runs/25085514106

Adds topology explain CLI, tray Explain Current Topology action, plain-language wizard presets, PowerToys layout guidance, and CTest coverage.