Crash reports: replayable, bounded, local, reachable by agents (#384)

Every panic (in a command, in the kernel, anywhere else) and every unclean
exit (abort, stack overflow, kill) leaves a report in a local crash folder:
message, file:line, a trimmed backtrace, version, commit, system and renderer,
the command and recent commands, and when possible the design and replay.json
that reproduce it (solvecraft-cli crashes replay <id>).

- Cost: nothing until the app installs the hook (tests, CLI and web never
  do); then one small journal line per top-level command of the design on
  screen, taken back with a truncate when the command changed nothing.
- Unclean exits: each run holds a lock on its journal; a journal nobody holds
  at the next start belongs to an app that died. Autosaves restart the
  journal from the autosaved design.
- Bounded: a crash's signature (place + message, numbers ignored) is counted,
  not rewritten; at most 5 new reports per run, 20 reports, 50 MB, 90 days;
  recovered kernel panics are pruned first.
- Agents: diagnostics.crash_reports / crash_report / crash_reports.clear
  commands, the MCP crash_reports tool, solvecraft-cli crashes, solvecraft
  --crash-log; diagnostics.crash_test (with SOLVECRAFT_CRASH_TEST) checks it.
- People: the Crash Reports window opens after a crash (Help > Crash
  Reports…) with a reviewed issue draft per report; nothing is sent.
- Release builds keep line tables for file:line in backtraces.

Tests: child processes that really panic in a command, in the kernel, on a
thread, and abort; dedup counts, limits, hostile folders, journal parsing,
the UI window and draft, the MCP tool. docs/crash-reports.md.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: bherbruck <brennen.herbruck@gmail.com>

crates/engine/src/recovery.rs

@@ -164,6 +164,8 @@ impl Autosaver {
                 self.has_entry = false;
             }
             self.last = None;
+            // Crash replays start from the saved file (or a new design) from here.
+            crate::crash::rebased(s, s.path.as_deref().map(Path::new), false);
             return Ok(false);
         }
         if self.last.as_ref().is_some_and(|l| Arc::ptr_eq(l, &s.doc) || **l == *s.doc) {
@@ -177,6 +179,8 @@ impl Autosaver {
         solvecraft_io::write_atomic(&file(&self.dir, &self.id, "json"), &meta, false).map_err(io)?;
         self.last = Some(s.doc.clone());
         self.has_entry = true;
+        // Crash replays start from this autosave from here.
+        crate::crash::rebased(s, Some(&file(&self.dir, &self.id, "solvecraft")), true);
         Ok(true)
     }