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>

docs/mcp.md

@@ -58,6 +58,7 @@ Claude Desktop (`claude_desktop_config.json`), bridged to a running app:
 | `screenshot` | `view?` (iso, top, front, back, bottom, left, right, home, fit), `path?`, `width?`, `height?`, `source?` (window, model) | A PNG image content block. Headless: CPU render fitted to the model. Bridged: the app window (default) or a model render with the app's camera. |
 | `export` | `path`, `format?` (step, 3mf, stl, stla, obj), `bodies?` | STEP, 3MF or mesh export. |
 | `undo`, `redo` | — | Undo / redo one change. |
+| `crash_reports` | `id?`, `limit?` | The crash reports on this computer, newest first; with `id`, the whole report (backtrace, command, recent commands, `design_path`/`replay_path`). See [crash-reports.md](crash-reports.md). |
 | `new_design` | `name?` | Start an empty design. |
 | `open` | `path` | Open a `.solvecraft` design, a STEP file (`.step`/`.stp`) as a new design holding its bodies (an Import base feature), or a 3MF/STL file as mesh bodies. |
 | `save` | `path?` | Save the design (to its current file without `path`). |