fix(fc2a): drop ruff target-version to py313 (runner has ruff 0.9.7)

The python-ci runner image ships ruff 0.9.7, which only recognizes
target-version values up to py313. Code still runs on Python 3.14;
this only affects which UP-rule suggestions ruff produces.

Durable fix is bumping RUFF_VERSION in CI-Runner/CI-python/Dockerfile
to 0.13+ and re-pushing the runner image — at which point we can flip
this back to py314. Inline comment in ruff.toml flags the future bump.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ruff.toml

@@ -1,4 +1,9 @@
-target-version = "py314"
+target-version = "py313"
+# Note: runtime is Python 3.14, but the python-ci runner image ships
+# ruff 0.9.7 which only knows target-version up to py313. Bumping the
+# runner image's RUFF_VERSION to 0.13+ would let us flip this back to
+# py314; until then py313 is the highest ruff accepts here. Code still
+# runs on 3.14; we just don't get UP suggestions for 3.14-only optimizations.
 line-length = 100
 
 [lint]