spyda: network topology engine for non-FWA stream networks (design placeholder)

[NewGraphEnvironment]

Problem

fresh queries work because fwapg encodes every stream segment with ltree watershed codes, blue line keys, and route measures. Nothing exists to assign these codes to LiDAR-derived channels, other jurisdictions, or custom networks.

Proposed Solution

spyda — new package that builds coded stream network databases from any source. Full design at inst/issues/design-spyda.md.

When NewGraphEnvironment/spyda is created, port the design doc as initial CLAUDE.md and close this issue.

Sequence

1. Build fresh manipulation functions first (Add .frs_resolve_aoi() internal helper for network-agnostic AOI resolution #34–Add frs_aggregate() for network-directed feature summarization #40 — they work against fwapg as-is)
2. Build spyda when ready
3. fresh's options() flexibility means no API changes when spyda networks arrive