Add jaccard() and jaccard_strengths() to Graph. Jaccard similarity
measures neighborhood overlap between linked nodes — nodes sharing
many neighbors get stronger links, nodes with no shared neighbors
get weak links.
New subcommand: `poc-memory graph normalize-strengths [--apply]`
Scales raw Jaccard (typically 0.0-0.3) to useful range via j*3
clamped to [0.1, 1.0]. Skips implicit temporal edges (strength=1.0).
Applied to 64,969 edges. Distribution is bimodal: large cluster at
0.1-0.2 (weak) and spike at 0.9-1.0 (strong), with smooth gradient
between. Replaces the meaningless 0.3/0.8 split from manual/agent
creation methods.
Co-Authored-By: Kent Overstreet <kent.overstreet@linux.dev>
dccc18b205