chore: remove the S1 community-basin probe and the jc dev-coupling

The S1 community-basin probe pooled ~1450 typed relation planes into one
undirected similarity graph and read a scalar phi as a "community-id earns
the mint" verdict — a flattening artifact (structure != similarity) that was
retracted. jc is the scientific crate; this empirical probe does not belong
coupled to it.

- delete crates/lance-graph/examples/p_community_basin_agree.rs
- remove the jc dev-dependency from crates/lance-graph/Cargo.toml + Cargo.lock
  (jc was reachable only via that dev-dep)
- the #722-only real-corpus variant + its schema.org data blob + python
  extractor never merged; dropped by resetting this branch to clean main

G0 harness (#716, no jc) is untouched. Board: EPIPHANIES E-S1-PROBE-REMOVED-1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016b33swuXE23hKtqxsHu9p1

Author: claude