Narrow Polars features to used operations

[rob-p]

Summary

Replace the broad/default Polars feature set with the operations grangers and its roers consumer actually use.

Retained features cover CSV writing, lazy frames, row extraction, struct and categorical columns, string concatenation, membership testing, and absolute value. Removed features are dataframe_arithmetic, checked_arithmetic, list_eval, regex, timezones, the blanket polars-ops request, and Polars defaults.

The temporal feature looks surprising but is intentional for Polars 0.53: enabling strings compiles an unconditional polars_time import in polars-expr without activating that optional dependency. temporal is the smallest working public Polars feature that supplies it; grangers itself does not use temporal columns. This is documented beside the dependency so it can be removed when the Polars wiring is fixed or upgraded.

Companion dependency cleanups: scverse/anndata-rs#43 and COMBINE-lab/af-anndata#3. Simpleaf's CI/LTO cleanup is COMBINE-lab/simpleaf#206.

Validation

• 24 grangers unit/integration tests pass
• the roers consumer builds, its tests pass, and its doctest passes against this branch
• the complete simpleaf dependency graph builds and all 77 simpleaf release-profile tests pass when combined with the companion narrow-feature branches