Build 26473667

This patch makes Windows launches predictable and adds the manual depth and
living-thermocline controls.

WINDOWS GRAPHICS

On some Windows 11 24H2/25H2 laptops with both NVIDIA and Intel graphics,
Chromium 156 can fail to initialise any GPU backend (`gl=none`) and leave the
game in software rendering. We tried the documented fixes — the install-folder
ACL grant, `--disable-gpu-sandbox`, `--no-sandbox`, `--ignore-gpu-blocklist`,
`--use-angle=gl`, updated Intel and NVIDIA drivers, and the Windows
high-performance preference — and none restored hardware acceleration on
affected machines. The same failure appears on older Electron versions, so it
is not something we can roll back. We keep the GPU-process sandbox disabled on
Windows — it is the switch that stopped the launch freeze — but it does not
bring hardware acceleration back.

Windows builds now default to software rendering for a stable launch. The game
is 2D and runs smoothly that way. On Windows, if your GPU works, MENU → DISPLAY
→ HW ACCEL turns acceleration back on and remembers the choice. To encourage
the discrete GPU, add SubSurvival.exe under Windows Settings → System → Display
→ Graphics and choose High performance.

QUALITY OF LIFE

• Manual depth entry: the HELM pane now has a depth box and SET button (plus
−10 / −1 / +1 / +10 nudges), so you can order any depth instead of only the
SURF / PD / 100 / TEST / CRUSH presets. It works just like the heading box.

• A living thermocline: the layer is no longer pinned at 120 m. Each scenario
has its own base depth, and storms deepen it while daytime heating shoals it.
The current depth is shown as LYR on the depth gauge.

• Logs are now bounded: launch.log and error.log are size-capped, and
chromium.log is only written when SUBSURVIVAL_DEBUG=1 is set.

If the window ever misbehaves after turning hardware acceleration on, the game
falls back to safe mode automatically.

Thanks for the reports and the logs.