feat(evaluators): add starts_with/ends_with mode to list evaluator

[lan17]

Summary

• add starts_with and ends_with match modes to the built-in list evaluator so policies can be expressed as plain prefix and suffix lists instead of synthesized regexes
• expose the new modes in the UI evaluator form and update the shared UI types
• expand evaluator coverage for prefix and suffix matching, allowlist-style no_match usage, path-like inputs, ordinary strings, escaping, and list-input semantics
• document the new list evaluator modes in the evaluator overview README

Scope

• User-facing/API changes: list evaluator configs now accept match_mode: "starts_with" and match_mode: "ends_with"; the UI exposes both as selectable options
• Internal changes: compile the new match modes into anchored prefix/suffix regexes in the evaluator implementation and add targeted evaluator tests
• Out of scope: changing prefix or suffix semantics to be path-boundary-aware; this PR preserves generic string-prefix and string-suffix behavior

Risk and Rollout

• Risk level: low
• Rollback plan: revert commits 5d29b8a, 4ddef38, 567f25f, and ef694b2, which removes the new match modes, coverage, and docs updates

Testing

• Added or updated automated tests
• Ran make check (or explained why not)
• Manually verified behavior

Checklist

• Linked issue/spec (if applicable)
• Updated docs/examples for user-facing changes
• Included any required follow-up tasks

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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