feat(navigation): verify editor selection mutations

[neusse]

Part of #395.

This replaces the cumulative #399 branch with the N4 change reconstructed directly on the merged N3 baseline (#492 / current main). It preserves the original contributor's authorship while removing the obsolete branch stack.

What this adds

• Semantic clear, add, and remove editor-selection mutations.
• Exact project, document, editor, and schematic sheet-instance binding before mutation.
• Stable KIID validation and operation-specific argument checks.
• Fresh before/after selection readback with exact-state verification.
• Structured readback_mismatch refusal when transport success does not prove the requested editor state.
• Typed IPC support for ClearSelection, AddToSelection, and RemoveFromSelection.

Boundaries

This remains intentionally limited to selection state. It does not add viewport activation, reveal, cross-probing, or raw/unverified IPC actions.

Reconstruction note

The sole cherry-pick conflict was in the structured error test inventory. The resolution preserves current-main UnsafeFileFallback and AmbiguousOpenBoard behavior while adding N4's independent ReadbackMismatch variant.

Evidence

• cargo test -p konnect-ipc --test mock_server_test — 55 passed, 1 ignored
• cargo test -p konnect-core editor_navigation --lib — 12 passed
• cargo xtask fix-doc-counts --check — passed
• cargo fmt --all -- --check — passed
• cargo clippy --workspace --locked --all-targets -- -D warnings — passed
• cargo test --workspace --locked --lib --tests — passed
• cargo test --workspace --locked --doc — passed

Original implementation: @dubesinhower (d6a78a6).