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/app/settings.rs

@@ -230,6 +230,33 @@ pub struct UserSettings {
     /// Interface language preference. `System` negotiates against the
     /// platform locale on every launch.
     pub language: crate::i18n::Language,
+    /// CLIPROMPTLINES: how many temporary prompt lines for a single command
+    /// are displayed above the command window (0–50, Registry, default 3).
+    #[serde(default = "default_clipromptlines", deserialize_with = "deserialize_clipromptlines")]
+    pub cliprompt_lines: i32,
+    /// Most-recently-inserted block names, most recent first, capped to 20.
+    /// Used to rank INSERT suggestions without touching the drawing file.
+    #[serde(default)]
+    pub block_mru: Vec<String>,
+    /// Insertion frequency per block name (uppercase key → count).
+    #[serde(default)]
+    pub block_freq: std::collections::HashMap<String, u32>,
+}
+
+fn default_clipromptlines() -> i32 {
+    3
+}
+
+fn deserialize_clipromptlines<'de, D>(de: D) -> Result<i32, D::Error>
+where
+    D: serde::Deserializer<'de>,
+{
+    let v = i32::deserialize(de).unwrap_or(3);
+    Ok(v.clamp(0, 50))
+}
+
+pub fn clamp_clipromptlines(v: i32) -> i32 {
+    v.clamp(0, 50)
 }
 
 impl Default for UserSettings {
@@ -268,6 +295,9 @@ impl Default for UserSettings {
             bg_color: None,
             paper_bg_color: None,
             language: crate::i18n::Language::default(),
+            cliprompt_lines: 3,
+            block_mru: Vec::new(),
+            block_freq: std::collections::HashMap::new(),
         }
     }
 }