Add create_canopy_fuel_grid_from_inventory to v2 SDK

[amarcozzi]

Wraps the generated create_inventory_canopy_grid endpoint in the hand-written v2 grids surface (fastfuels_sdk/v2/grids.py), following the create_<thing>_grid_from_<source> convention.

What

create_canopy_fuel_grid_from_inventory(inventory, ...) derives canopy fuel bands (cbd, cbh, chm, cc, and optionally cfl) for each cell directly from a completed tree inventory (live trees only, matching FuelCalc). It accepts an Inventory object (its domain is read from the object) and returns a pending Grid.

The endpoint's many method choices are exposed as friendly kwargs with sensible defaults that map onto the generated union models:

• biomass source: biomass_equations (nsvb / jenkins / brown_1978) vs. biomass_column (precomputed available fuel)
• available fuel (allometry only): foliage_fraction, branchwood_fraction, branchwood_size_partition
• species inclusion, crown-class adjustment, min_tree_height
• vertical/horizontal distribution, layer_depth
• max crown radius source: max_crown_radius_equations vs. max_crown_radius_column
• per-band reduction methods cbd / cbh / chm / cc: each accepts a method-name string (built with default parameters) or a prebuilt method object (e.g. CanopyCbhPercentile(percentile=25)) for non-default parameters
• alignment via output_resolution_m / align_to / resampling (native is not supported by this endpoint)

Generated client code is imported, not modified. The function is exported through ff.grids.* via grids.py's __all__.

Tests

tests/v2/test_grids.py gains TestCreateCanopyFuelGridFromInventory, mirroring the DUET test structure: offline request-building/validation tests (monkeypatched endpoint) plus a live end-to-end test.

• Offline unit tests: 11 passed.
• black and flake8 pass (pre-commit clean).
• Live test (test_create_live): passed against the live API (~69s) — creates the grid from the shared tree-inventory fixture, waits to completion, asserts the five bands, and reads the cbd array.

Closes #196