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>

src/modules/annotate/mleader_edit.rs

@@ -476,3 +476,10 @@ fn preview_wire(pts: &[Vec3]) -> WireModel {
 
 // Silence unused-import warning for MultiLeader and LeaderLine if not used in all paths
 fn _uses_ml_types(_ml: &MultiLeader, _ll: &LeaderLine) {}
+
+
+// ── Autocomplete registry ─────────────────────────────────
+inventory::submit!(crate::command::CommandRegistration { names: &["MLA", "MLEADERADD"] });  // MLeaderAddCommand
+inventory::submit!(crate::command::CommandRegistration { names: &["MLAL", "MLEADERALIGN"] });  // MLeaderAlignCommand
+inventory::submit!(crate::command::CommandRegistration { names: &["MLC", "MLEADERCOLLECT"] });  // MLeaderCollectCommand
+inventory::submit!(crate::command::CommandRegistration { names: &["MLEADERREMOVE", "MLR"] });  // MLeaderRemoveCommand