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/control-protocol.md

@@ -75,7 +75,7 @@ unit regardless of the design, pass an expression with one: `"value": "50 mm"` o
 | `ui.file` | `path`; `insert?`: bool | starts an interactive background Open or Insert; poll `ui.inspect.file_busy` for completion; the window stays responsive |
 | `ui.home` | `open?`: bool; `sample?`: index | the start page: show or hide it, open a built-in sample (once built); returns `open` and the recent designs |
 | `ui.shortcut` | `command`, `key?`, `replace?` | a command's key, or rebinds it (`""` clears; a key another command uses is refused unless `replace`) |
-| `ui.help` | `item?`: `about`, `shortcuts` (read only), `report` (copies diagnostics) | the version, commit, build date and diagnostic text |
+| `ui.help` | `item?`: `about`, `shortcuts` (read only), `report` (copies diagnostics), `crashes` (the Crash Reports window) | the version, commit, build date and diagnostic text |
 | `ui.prefs` | any of `default_units`, `nav` (`fusion`, `solidworks`, `inventor`, `alias`, `tinkercad`, `openscad`), `zoom_reverse`, `zoom_to_cursor`, `smooth_wheel_zoom` (default true), `trackpad_pan` (default true: two-finger scroll pans, pinch zooms), `orbit_cursor`, `look_at_anim`, `look_at_speed`, `msaa`, `length_decimals`, `angle_decimals`, `theme` (`dark`, `light`, `system`), `language` (`en`, `ja`; see [localization](localization.md)), `ui_scale`, `up_axis` (`z`, `y`), `offer_stand_up`; `open` (a page: General, Navigation, Keyboard Shortcuts, Design, Graphics, Sketch, Selection) opens the Preferences dialog there; `button`: `ok`, `cancel`, `apply`, `defaults`; `stand_up: true` stands up a just-opened Y-up file | sets preferences (kept between runs), returns them all plus `dialog` (the open page or null), `dark` and `stand_up_offer` |
 | `ui.capture` | `action?`: `capture`, `revert`, `cancel` | answers the Capture Position question (asked when a command starts or the design is saved while components were moved without capturing); without `action`, what waits |
 | `ui.window` | `action`: minimize, maximize, restore, toggle, close | what the title bar's caption buttons do (on Windows and Linux the application bar is the title bar); close asks about unsaved designs first |