v0.4.7 — paths.rs split, analyze_symbols decomposed

Refactor: paths.rs → paths/ module directory

739-line paths.rs split into 3 focused modules:

Module	Responsibility	LOC
paths/mod.rs	CLI entry point: run, PathsArgs, write_html	145
paths/bfs.rs	BFS path-finding + tree construction helpers + BFS tests	224
paths/signals.rs	Signal, analyze_symbols, render functions + signal tests	406

analyze_symbols (was 150-line function) split into:

• signals_for_path_shape — path depth + cross-file boundary
• signals_per_symbol — lock/await, block_on, loop, complexity, hotspot per symbol
• signals_for_terminal — async handoff + external boundary at path end

No behavior change. 71 tests pass.