Story: Decode WKT curve geometries #9

Goal

Add WKT decoding support for LINESTRING and MULTILINESTRING geometries.

The decoder must parse their coordinate sequences and nested structures, preserve the represented coordinate dimensions, and construct the corresponding immutable spatial objects while enforcing the applicable structural constraints.

Acceptance criteria

• LINESTRING is decoded into the corresponding spatial object.
• MULTILINESTRING is decoded into the corresponding spatial object.
• XY, XYZ, XYM and XYZM coordinates are supported.
• EMPTY representations are supported.
• Coordinate values, ordering and dimensions are preserved.
• Invalid or structurally inconsistent representations are explicitly rejected.
• No unsupported spatial information is silently discarded or converted.
• Unit tests cover supported types, dimensions, EMPTY, and invalid representations.
• The standard test and quality suites pass.

Out of scope

• Point, surface and collection geometry types.
• EWKT and SRID-prefixed representations.
• Coordinate reprojection.
• Implicit geometry or dimension conversion.