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 <[email protected]>
Co-authored-by: bherbruck <[email protected]>

AGENTS.md

@@ -36,7 +36,12 @@ People trust SolidCraft with their designs; a crash loses their work. **This out
   `solvecraft_kernel::guard`, which turns a panic into `KernelError::Internal`.
 - **Last-resort guard:** `Session::execute` runs every command under `catch_unwind`; an escaped
   panic restores the design and reports `EngineError::Internal`.
-- **Prove it:** every crash fix lands with a regression test (see `hostile_params_never_panic`).
+- **Crash reports:** the desktop app writes every panic and every unclean exit to a local crash folder,
+  with the design and the commands that reproduce it (`solvecraft_engine::crash`, docs/crash-reports.md).
+  When someone says the app crashed, look there first: `solidcraft-cli crashes`, `crashes show <id>`,
+  `crashes replay <id>` (or the `diagnostics.crash_reports` command / MCP `crash_reports` tool).
+- **Prove it:** every crash fix lands with a regression test (see `hostile_params_never_panic`); a
+  crash report's `design.solvecraft` + `replay.json` is the test's starting point.
 - Every production crate root carries
   `#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]`.