Add wall parametric editing and gizmos

Walls gain in-viewport parametric editing matching the door/window/stair
UX: drag handles for length, height, slope (x-angle), layer baseline
cycle, plus cursor-anchored quality-of-life operators (split at cursor,
extend to cursor, extend height, rotate 90, toggle openings) and
two-object state-machine gizmos (unjoin / merge / join-corner /
extend-to-wall / extend-vertically / add-opening).

Wall enters tool.Parametric.EDIT_TYPES, so save-time auto-commit,
GizmoPreferencesWall registration, and the in-progress-edit predicates
all light up automatically through the registry plumbing landed two
commits back.

The three-layer commit model (drag -> BIMWallProperties -> bmesh
preview -> Finish -> single ifc.run) means dragging a handle through
hundreds of intermediate values produces zero extra IFC entities. A
no-op enable->finish round-trip is byte-identical. The snapshot diff
in FinishEditingWall skips unchanged params.
_commit_active_wall_edit_if_any ensures cursor-anchored operators see
committed geometry, not the draft preview box.

Also lands the `prompt_auto_commit_parametric_edits` BoolProperty on
BIM_ADDON_preferences (consumed by the auto-commit dialog landed in
the framework commit) and refactors
`draw_{door,window,stair}_gizmo_parameters` into a shared
`_draw_parametric_gizmo_parameters` helper that the new
`draw_wall_gizmo_parameters` reuses. This commit and the framework
commit are stacked - the framework commit references the BoolProperty
defined here, so they must land together.

Tests cover pure math (core/test_model.py), DimensionGizmoConfig text
formatter, GizmoWallExtendVertically.poll() preconditions, and the
refresh_post_commit cache-invalidation regression. BDD scenarios in
model.feature cover the edit triad, auto-commit on save, and the
two-object gizmos. Documentation added to creating_walls.rst.

Generated with the assistance of an AI coding tool.

src/bonsai/docs/guides/authoring/basic_modeling/creating_walls.rst

@@ -51,6 +51,62 @@ To use these tools:
 2. Use the appropriate shortcut or select the tool from the top bar.
 3. Follow the on-screen prompts or adjust parameters as needed.
 
+Interactive Parametric Editing
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Selected walls expose an in-viewport parametric edit mode that mirrors the door /
+window / stair pen-icon UI:
+
+1. Select a single wall. A pen (Edit Wall) icon appears next to the wall in the
+   3D viewport, and a matching ``Edit Wall`` button is available in the
+   ``Parametric Geometry`` tab of the N panel.
+2. Click the pen icon (or the panel button) to enter edit mode. Dimension
+   gizmos for length, height, slope (x-angle) and the layer offset baseline
+   appear around the wall.
+3. Drag any handle to update the value. Dragging only modifies the in-progress
+   draft — the IFC file is not touched until you commit, so dragging a length
+   handle through many intermediate values produces zero extra IFC entities.
+4. Click the green ✓ icon to commit; click the red ✗ to discard. Pressing the
+   ✓ icon on a wall that hasn't been dragged is a true byte-identical no-op —
+   the IFC file is unchanged.
+
+While editing, additional gizmos surface based on context:
+
+- **Cycle Baseline**: cycles the layer offset baseline (Exterior → Centreline →
+  Interior). Shift+click cycles in reverse.
+- **3D-cursor scissors**: appears when the 3D cursor sits on the wall axis;
+  clicking splits the wall at the cursor's projected X.
+- **3D-cursor extend (horizontal)**: appears when the 3D cursor sits beyond the
+  wall axis; clicking extends the wall to the cursor's projected X.
+- **3D-cursor extend (vertical)**: appears when the 3D cursor sits above /
+  below the wall; clicking extends the wall's height to the cursor's Z.
+- **Rotate 90°**: rotates the wall around its Z axis.
+- **Show / hide openings**: toggles opening fill visibility (doors and windows).
+
+When two walls are selected, the gizmo switches to a state-aware icon at their
+common point:
+
+- Already joined → an Unjoin icon at the shared corner.
+- Collinear (same axis line) → a Merge icon at the boundary midpoint.
+- Joinable corner → a Join icon at the floor + an Extend-To-Wall icon at the
+  active wall's top.
+
+When a wall and a slab (LAYER3 element) are selected, an Extend-Vertically icon
+appears at the wall's origin / slab elevation; clicking dispatches
+``bim.extend_walls_to_underside``.
+
+When a wall and a non-wall, non-slab object are selected, an Add-Opening icon
+appears above the wall at the other object's projected X.
+
+Auto-commit on save
+~~~~~~~~~~~~~~~~~~~
+
+Pressing Ctrl+S (or running ``bim.save_project``) while any wall is mid-edit
+flushes every pending parametric draft first — the same Apply-Wall-Edits the ✓
+icon performs, scoped per wall. The IFC saved on disk reflects the values the
+user dragged, not the snapshot taken when edit mode was entered. Each commit
+produces its own undo entry, so Ctrl+Z walks back through commits individually.
+
 Aligning Walls
 ^^^^^^^^^^^^^^