Engine: crash reports, a log file and bug report drafts (#107)

crash: a panic hook and a locked per-run command journal (adapted from
SolidCraft's crash reports). A panic in a command becomes a report with
the model from before it and the command; one outside commands, or an
unclean exit found at the next start (abort, segfault, a crash in a
graphics driver, a kill: what #248 needs), a report with the model the
journal starts from (autosave, file or a copy) and the commands since,
the last control request and the dead run's log lines. Reports are
bounded, deduplicated by signature and replayable (crash::replay, with
writes confined to a scratch folder). The crash folder follows the
automation temp area in --control and CI runs.

logfile: a small size-rotated file logger behind the log facade.

bug_report: GitHub bug-form drafts. Version, OS and what happened by
default, home folder shown as ~; the command journal only with Share my
session, the model only with Include the model as well; a session too
long for the link becomes a file to attach and the clipboard text.

Commands: diagnostics.crash_reports, diagnostics.crash_report,
diagnostics.bug_report (Tools › Help, with its icon) and
diagnostics.crash_test (FIELDCRAFT_CRASH_TEST=1 only).

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

crates/engine/src/catalogue.rs

@@ -591,6 +591,14 @@ pub static CATALOGUE: &[Capability] = &[
     ),
     ready("edit.undo", "Undo", Tools, "History", "Undo the last command that changed the model"),
     ready("edit.redo", "Redo", Tools, "History", "Redo the command undone last"),
+    ready_more(
+        "diagnostics.bug_report",
+        "Report a Bug",
+        Tools,
+        "Help",
+        "Draft a GitHub bug report with the version, the OS and the last error; you review it, and nothing is sent until you submit it",
+        &["diagnostics.crash_reports", "diagnostics.crash_report", "diagnostics.crash_test"],
+    ),
 ];
 
 /// The catalogue entry with this id.