feat: add smooth interactive axis view and diagonal snapping

ROADMAP.md

@@ -61,6 +61,13 @@ headline counts in-scope tabs only and lists the deferred ones separately.
 | M14 | Configurations: a table of rows (parameter expressions and feature suppressions per row) switched with config.activate (undoable, all or nothing), kept through parameter renames and feature deletes (config.configure, config.table, config.column/row/activate). Per-row body materials and appearances (library looks, custom colour/opacity and clearing overrides), undoable activation and save/reopen: done. Ordered typed configuration rules, atomic validation and structured rule editing: done. Component appearance and certified semantic face style columns, atomic preview/apply and independent-copy remapping: done. Exact constructed sketch-side and immutable imported-face lineage now preserve legacy names and reject retargeting. Left: ambiguous shifted/two-sided caps | in progress | 4 |
 | M13 | Never lose work: atomic saves (temporary file, flush, rename; a crash at any moment leaves the old file or the new one) with the replaced version kept as `<file>.bak`; autosave of unsaved changes to the recovery folder every 5 minutes (preference) and after big operations, only when something changed; "Recover unsaved design?" on the next launch (`doc.recovery_list`, `doc.recover`, `doc.recovery_discard`); a kill-mid-save test (process killed while saving a 0.5 MB design 25 times). File format: `"format": "solvecraft/11"`, older formats upgraded step by step (`doc::format`), newer ones refused with a message, out-of-range numbers and broken placements refused; a corpus of designs saved by M0, components-era, joints-era and current builds (apps/solvecraft-cli/tests/corpus) that must open and evaluate as saved; damaged and hostile variants (truncation, bit flips, hostile values, removed keys, repeated features, deep nesting) never panic | done | 6 |
 
+## View navigation
+
+- Compact clickable signed X/Y/Z axis tips, smooth drag-to-orbit, and Shift-orbit snapping
+  to 26 standard and diagonal views. Pointer motion accumulates independently of a lightly
+  damped spring, with a boundary margin to prevent flicker. Z-up/Y-up and the nearest square
+  top/bottom heading are preserved. Diagonals include 45-degree edge and isometric corner views.
+
 ## Known limitations
 
 - Fillets and chamfers: constant, variable-radius and chord-length fillets; a radius per edge,