Support a project config file for custom claim/evidence/hedge patterns

[Yesol-Pilot]

The claim / evidence / hedge regex families live in src/neo_evidence_gate/rules.py. Teams should be able to add or override patterns per project without forking.

Scope

• Read an optional .neo-evidence-gate.toml (or a [tool.neo-evidence-gate] table in pyproject.toml).
• Let it extend the default claim / evidence / hedge lists (and optionally override).
• Wire it through check_text() and the CLI.
• Mirror the style of tests/test_gate.py with tests for merged patterns.

Constraints

• Keep zero required runtime deps — use stdlib tomllib on 3.11+, with a graceful path for 3.9/3.10.

Good first issue: self-contained, clear seam in rules.py, existing tests to imitate.