[omartelo]

What happened

A Windows lich.log ends mid-session — no window closed, exiting, no
chromium shell error, no transport listener stopped. The window stayed on
screen still rendering its terminal, but nothing updated again and a reload
found nothing listening.

Two things were wrong, and the second is why the first went undiagnosed for so
long.

The crash

processCwd (internal/terminal/cwd_windows.go) walks the child's PEB and
reads CurrentDirectory.DosPath out of that process's memory.
NTUnicodeString.Length is a byte count that x/sys documents as "should
always be even" — a should about a value read from another process, which a
32-bit child or one exiting mid-walk does not honour.

The guard only rejected zero. An odd length sized the buffer to zero and the
read went straight into &buf[0]:

buf := make([]uint16, dos.Length/2)          // Length=1 -> len 0
readMemory(h, ..., unsafe.Pointer(&buf[0]), ...)  // index out of range [0] with length 0

That runs on the bare goroutine watchCwd spawns per session, every 300ms, so
the panic ended the process. net/http recovers panics in its handlers, which
is why RPC and WebSocket traffic never showed this — the poller was outside
that net.

The length now goes through dosPathRunes, which refuses anything a UTF-16
buffer cannot have. It sits in the untagged cwd.go, following
windowsBrowserCandidates in internal/chromium, so the guard is tested on
every OS rather than only where it runs.

Why the log said nothing

The runtime prints a panic to stderr. The Windows build is -H=windowsgui
(Taskfile.yml), so there is no console and fd 2 goes nowhere; slog never sees
a panic, so the file half of the log was never going to carry it.

logging.Init now calls debug.SetCrashOutput with the log file it already
holds. Verified end to end — the child half of the new test writes a real trace
into lich.log:

panic: crash probe [recovered, repanicked]

goroutine 35 [running]:
...
github.com/omartelo/lich/internal/logging.TestInitRoutesPanicToLogFile(...)

Test plan

• gofmt -l . and go vet ./... clean
• go test ./... — 531 pass
• New tests green under -race: TestDosPathRunesRejectsUnusableLengths,
  TestInitRoutesPanicToLogFile (subprocess, asserts the trace lands in the
  file)
• Cross-compile loop GOOS=linux|darwin|windows — go build + go vet clean
• biome check, vitest run (501 pass), tsc && vite build — untouched by
  this change, run for the gate
• ci:os — the backend suite on a real Windows runner
• Manual: run on Windows, open a session, confirm it survives past the point
  it used to disappear

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