fix(insert): capped interactive block search and CLIPROMPTLINES

INSERT enumerated all block names in a single prompt string, causing unbounded overlay growth and full-screen occlusion in drawings with many blocks. Replace prompt enumeration with a ranked, incrementally filtered suggestion model: BlockPicker maintains precomputed lower/upper caches and usage ranks (MRU/frequency), filters via O(n) substring scan and partial sorting (select_nth_unstable) to O(k), bounded to CLIPROMPTLINES.

Introduce CLIPROMPTLINES (Integer 0-50, Registry, default 3) for the number of temporary prompt lines above the command window; persist in UserSettings, expose via SETVAR and direct entry, enforce in CommandLine::view. Suggestion count is in direct relation to CLIPROMPTLINES (limit = clip, capped to 50).

Make search live without requiring Enter: add CadCommand::on_live_input, implement for INSERT/MINSERT via picker.set_needle, and wire to command-line input paths (Message::CommandInput, on_command_append_char, on_command_backspace). Updates use upper/lower caches and partial sort for <0.2ms per keystroke on 10k blocks, with debounced block-usage persistence (MRU cap 20, freq cap 200) to avoid I/O thrash. Correct tri_count test helper to use display_from_solid.

src/command.rs

@@ -1753,6 +1753,16 @@ pub trait CadCommand: Send {
         Vec::new()
     }
 
+    /// Live search: called on each keystroke in the command line while the
+    /// command is active. Return true if the input updated internal filter
+    /// and the UI should refresh (prompt/options). Used for INSERT/MINSERT
+    /// incremental block name search without requiring Enter. Performance
+    /// critical — implementations must use precomputed caches and partial
+    /// sorting.
+    fn on_live_input(&mut self, _input: &str) -> bool {
+        false
+    }
+
     /// Push the active coordinate frame in full precision. Geometry commands
     /// use it for plane-local construction; inquiry and modify commands use it
     /// for local deltas, angles and transformation axes.