Fix Clifford identification tolerance propagation

[qciaran]

Summary

• propagate caller-provided tolerances through matrix fallback and global-phase normalization
• make the normalization threshold independently configurable when required
• recognize identity rotations symmetrically around positive and negative multiples of tau
• expose the Clifford identification API from pecos.analysis
• make the deprecated pecos.tools.find_cliffs module re-export the canonical implementation instead of maintaining a duplicate

Validation

• 64 focused Clifford identification tests pass
• 75 combined Clifford and existing PyPHIR name-resolution tests pass
• all canonical matrices round-trip through identification
• conversion-table entries match table-disabled matrix fallback
• boundary coverage includes negative-near-zero angles, positive and negative tau multiples, caller-selected tolerances, and configurable normalization thresholds
• changed-file Ruff and Black checks pass
• uv lock --check passes