feat(commandline): autocomplete suggestions + inventory-based registry

Type-as-you-go suggestion popup above the input that filters known
command names by substring (so `LEADER` surfaces both LEADER and
MLEADER). Up / Down navigates the list, Enter dispatches the
highlighted entry, clicking a row dispatches directly. Esc on a
non-empty input clears the buffer instead of escalating to
command-cancel.

The name corpus comes from `inventory::submit!` blocks placed next
to each `CadCommand` impl rather than a hand-maintained static list.
Adding a new interactive command means dropping one `inventory::submit!`
line in its own module file — the autocomplete picks it up at the
next compile. 98 submissions seeded across 60 module files;
`command::all_registered_command_names()` flattens them at runtime.

One-shot dispatch arms in `app/commands.rs` (NEW, OPEN, SAVE, UNDO,
…) don't have a `CadCommand` impl and are therefore absent from
autocomplete by design.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Cargo.lock

@@ -12,6 +12,7 @@ dependencies = [
  "glam 0.33.0",
  "iced",
  "image",
+ "inventory",
  "open",
  "printpdf",
  "rayon",
@@ -2311,6 +2312,15 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "inventory"
+version = "0.3.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4f0c30c76f2f4ccee3fe55a2435f691ca00c0e4bd87abe4f4a851b1d4dac39b"
+dependencies = [
+ "rustversion",
+]
+
 [[package]]
 name = "is-docker"
 version = "0.2.0"