chore(agent): modernise base → Ubuntu 24.04 / Python 3.12 / CUDA 12.9

Bump the GPU-agent base image from 12.4.1-cudnn-runtime-ubuntu22.04 (Python 3.10,
CUDA 12.4, early-2024) to 12.9.2-cudnn-runtime-ubuntu24.04:

- Ubuntu 24.04 LTS → Python 3.12 — one modern runtime, no more 3.10.
- CUDA 12.9 + cuDNN 9 — current within the CUDA-12 / cuDNN-9 line that the
  default onnxruntime-gpu wheel AND torch cu124 are built against. NOT CUDA 13:
  ONNX Runtime's CUDA-13 support is still nascent (separate wheels + open
  "Unsupported CUDA version: 13" reports), and torch bundles cu124 anyway. The
  GPU (Ampere/Ada, 12 GB) is fine on either — this is a library-alignment call,
  not a hardware limit.
- PIP_BREAK_SYSTEM_PACKAGES=1: 24.04 marks system Python externally-managed
  (PEP 668); a single-purpose container owns its environment, so global installs
  are fine and simplest.
- agent/ruff.toml pinned to py312 (was py310) so CI lints against the real
  runtime; from __future__ import annotations stays (PEP 649 lazy annotations
  are 3.14, so self-refs still evaluate on 3.12).

CI builds the image but has no GPU — validate on the desktop after pull that it
starts and loads CUDAExecutionProvider (not CPU fallback).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

agent/fc_agent/app.py

@@ -15,7 +15,7 @@ from .worker import Worker
 # Bump on every agent change. The page embeds this and /status reports it; the UI
 # warns to reload when they differ — so a stale browser-cached page can't be
 # mistaken for "the new image didn't deploy". (Belt-and-braces with no-store.)
-VERSION = "2026-06-30.6 · submit-retry+py310"
+VERSION = "2026-06-30.7 · ubuntu24.04-py312-cuda12.9"
 
 logbuf.install()
 cfg = Config.from_env()