Remove assumptions that radar sweeps start at zero degrees

[danielway]

Scope

Audit acquisition, decoding, probing, analysis, projection, and rendering for assumptions that a sweep starts at 0 degrees or covers a uniform full rotation. Introduce explicit angular coverage that supports both full rotations with arbitrary first radial and partial sectors, including sectors crossing 360/0 degrees.

Behavior

• Preserve actual radial azimuths and distinguish chronological first radial from sorted/render order.
• Missing sectors remain missing; they are not stretched, interpolated across, or treated as below-threshold data.
• 2D and Globe surface rendering support compatible partial sectors.
• Volume rendering and analysis tools declare and enforce their coverage requirements; unsupported partial inputs are disabled with clear capability state rather than miscomputed.

Non-goals

• Adding Level III decoding or new product identities.
• Inferring data in unobserved sectors.

Acceptance criteria

• Full rotations beginning at a non-zero azimuth decode, cache, probe, composite, and render correctly across wraparound.
• Partial sectors, including a 350-to-30-degree sector, preserve gaps and render only observed coverage in supported paths.
• Spacing and neighbor decisions use actual azimuths rather than 360 / radial_count.
• Timeline/sweep metadata retain chronological start and coverage accurately.
• Unsupported analysis/view combinations are capability-gated with actionable UI state.
• Fixtures cover non-zero full rotation, wraparound sector, non-wrap sector, nonuniform spacing, and gaps; existing full rotations remain unchanged.

Parent: #35; blocks #180.