Command line: a bare system variable name runs SETVAR on it (part of U10) (#799)

* Command line: a bare system variable name runs SETVAR on it (part of U10)

Typing ORTHOMODE, PICKADD and the like at the command line returned
"unknown command". Session::start now falls back to SETVAR with the name
already entered when the text is not a command but is a known variable;
dash, dot and underscore prefixes never mean a variable, and real
commands still win. Read-only variables print their value, and the
transparent form ('OSMODE) resumes the interrupted command.

Checked: fmt, clippy, test, assets, layers and wasm pass; also driven
through the control channel in the running app.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

* Tests: every variable name, command collisions and hostile input for bare SETVAR

Covers each variable SETVAR lists: a name that is not a command starts SETVAR
(or prints a read-only value), a name that is also a command keeps the command,
and odd input (lone apostrophes, NUL, wide characters, a 1 MiB name) never
panics and leaves the session usable. Disabling the fix makes all three new
and old tests fail.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

---------

Co-authored-by: Claude Sonnet 5.5 <[email protected]>
Co-authored-by: Brandon Thomas <[email protected]>

docs/gaps.md

@@ -1,6 +1,6 @@
 # Where CADCraft falls short of AutoCAD
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-12 · **Change:** minor (Hatch and Gradient / Hatch Edit dialogs landed; F13 narrowed) · **Target:** Autodesk AutoCAD 2027
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-12 · **Change:** minor (a bare system variable name typed as a command runs SETVAR; U10 narrowed) · **Target:** Autodesk AutoCAD 2027
 
 Every known shortfall, one row each, ranked within each section by user impact. This is the work
 list: agents pick from here (top of a section first), and remove or update a row in the same PR
@@ -57,7 +57,7 @@ Detail and evidence: [ui-parity.md](ui-parity.md).
 | U5 | Grip menus open on right-click only (no hover menu, no Ctrl to cycle the options); no multifunctional grips on dimensions, MLEADER, hatches or text; Add Vertex on an arc segment straightens it. Hot-grip options (Base point, Copy, Undo, Reference, eXit), multiple hot grips and the polyline/line/arc grip menus landed (#425) | Low-medium | 2–4 |
 | U6 | Selection: lasso; selection cycling (a list of overlapping objects, SELECTIONCYCLING); the CLass keyword; isolation saved with the drawing (OBJECTISOLATIONMODE 1) and the status-bar isolate button. Press-drag windows (#63), the W, C, F, WP and CP keywords (#226), BOX, AUto, SIngle, Multiple, Group, Add, Remove and Undo, SELECTSIMILAR, and ISOLATEOBJECTS/HIDEOBJECTS/UNISOLATEOBJECTS (#428) landed | Medium | 3–5 |
 | U7 | Right-click menus: no in-place layout tab rename or Move or Copy dialog, no Select All Layouts, no Paste to command line; palette menus are on the Layers rows and the Properties background only. The command menu (held right-click: Enter, Cancel, Recent Input, options, Snap Overrides, Pan/Zoom), the selection menu with object edits, command line, drawing tab, layout tab and palette menus landed (#512) | Low | 1–2 |
-| U10 | SETVAR covers about 150 of ~1,000 variables (UNDO options, MREDO and UNDOCTL, and header variables such as CIRCLERAD, OFFSETDIST, POLYSIDES, HPNAME and the dimension variables in SETVAR ? landed, #461); typing a variable name as a command doesn't run SETVAR | Low-medium | 3–5 |
+| U10 | SETVAR covers about 150 of ~1,000 variables (UNDO options, MREDO and UNDOCTL, and header variables such as CIRCLERAD, OFFSETDIST, POLYSIDES, HPNAME and the dimension variables in SETVAR ? landed, #461; typing a bare variable name as a command runs SETVAR on it) | Low-medium | 3–5 |
 | U11 | MVIEW Restore (a saved viewport configuration into a layout); VIEW Orthographic, UCS and background settings; view twist is kept but not shown (Zoom Realtime and Dynamic, ZOOMFACTOR, named views (VIEW) and tiled model viewports with saved configurations (VPORTS) landed in #463) | Low | 1–2 |
 | U12 | Workspaces, navigation bar, CUI customisation, alias editor, ViewCube drag (#7) | Low-medium | 15–25 |
 | U13 | `.dxf` from Finder fails to open on macOS (#158) (window controls fixed, #161) | Medium | 1–2 |
@@ -147,6 +147,7 @@ Detail: [localization-parity.md](localization-parity.md).
 | Date | Change | Summary |
 |---|---|---|
 | 2026-10-12 | minor | Hatch and Gradient dialog (HATCH, GRADIENT; HPDLGMODE) and Hatch Edit dialog (HATCHEDIT, right-click, double-click a hatch): F13 narrowed to Preview, Inherit Properties and boundary add/remove in edit mode |
+| 2026-10-12 | minor | A bare system variable name typed at the command line (ORTHOMODE, GRIDMODE…) runs SETVAR on that variable, as in AutoCAD; U10 narrowed |
 | 2026-10-12 | minor | SCRIPT command reading `.scr` files landed (runs a file through the same script engine as CLI/MCP; nested scripts refused): E2 removed |
 | 2026-10-11 | minor | Refreshed for merged features: code pages (#505), tracking leftovers (#441), dynamic input/grip input (#519, #425) and SPLINEDIT Join/Add/Elevate (#559) closed their top-10 rows (top 10 now has 6 rows until the next review re-ranks); MULTILEADER (#459) and xrefs (#525) narrowed rows 1 and 4; F1 narrowed to the remaining stubs (#558, #559, #547); F5, F7, F9, F12, F14, F15, F17, F20, F22, U5, U7, U10, FF2, FF4, FF10 narrowed; F18, U2, U8, U9 removed (done); U13, S3, S4, P1 updated for merged fixes |
 | 2026-10-11 | minor | German interface catalog landed: L1 row count 936 → 989, L2 narrowed (de done; 40–60 → 35–55 h) |