ui: jobs with progress, refusals listed, datum preview, form filters and defaults

- A solve or a mesher runs as a job with one progress mechanism: the overlay
  shows the step, stage, count and elapsed time with a bar when bounded, OK
  waits while it runs, and the status sums it up (elements, smallest angle,
  time) (#322, #357).
- Over the control channel such a command is a job too: answered when it
  ends however long it runs, or at once with wait: false, then job.status,
  job.wait, job.cancel; ui.inspect gives job; MCP waits for it (#367).
- A command that cannot run yet lists what it misses in the context panel,
  each with a button to the command that provides it (#323).
- A cancelled or refused solve stays in its workspace (#324, test).
- A mesher form starts from the parameters of the mesh it would replace (#343).
- Seed Edges and edge/vertex/face datum points switch the selection filter
  while open and restore it (#341).
- Datum forms draw the datum live, the Partition form shows its datum, and
  new datums and partitions get the next free name (#347).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/mcp/src/backend.rs

@@ -164,9 +164,10 @@ impl Remote {
             match TcpStream::connect_timeout(&sa, Duration::from_millis(800)) {
                 Ok(s) => {
                     s.set_nodelay(true).ok();
-                    // Meshing and solving big models take a while; the app answers a request it
-                    // has not finished within 60 s with a timeout of its own.
-                    s.set_read_timeout(Some(Duration::from_secs(600))).ok();
+                    // Meshing and solving big models take as long as they take: the app answers
+                    // a solve or a mesher when its job ends (docs/control-protocol.md, Jobs), and
+                    // a closed app closes the connection.
+                    s.set_read_timeout(None).ok();
                     let read = s.try_clone()?;
                     self.conn = Some((BufReader::new(read), s));
                     return Ok(());