feat: tile isolated reshapes with integral row mappings

[asteinh]

• The partitioner tiles a single-op Reshape stage when the leading block count is equal on both sides and every band, the last one included, maps to whole output rows. Band sizes are multiples of Co / gcd(Ci, Co). Matrix-row axes are tried first, then stored axis 1.
• A Reshape that changes the block count, reorders elements or sits inside a chain stays untiled.
• 14 of the 18 Reshape stages in the TFLite corpus that exceeded 256 bytes now tile there. 7 of the 12 affected models compile at 256 bytes and match TFLite Micro byte for byte.

Needs the runtime branch of the same name.