chore(core): remove orphaned, never-compiled test files

[dsmfa10]

Problem

Two test files are not declared by any mod, so the compiler never built or ran
them. They are dead weight and, worse, both contain code that would not even
compile if wired in (giving a false sense of test coverage):

1. src/core/token/policy/policy_validation/complexity_tests.rs

   • No mod complexity_tests; exists anywhere (policy_validation.rs declares
     only mod tests). Confirmed via workspace grep.
   • Its assertions check for a warning substring ("exceeds 80%") that the code
     no longer emits (policy_validation.rs emits "over 80% of limit"), so the
     tests would fail if ever compiled.

2. src/cpta/tests/mod.rs + src/cpta/tests/policy_tests.rs

   • cpta/mod.rs never declares mod tests, so the whole tests/ directory is
     orphaned.
   • policy_tests.rs constructs PolicyRole.permissions / OperationRestriction. allowed_operations (both Vec<String>) with Operation enum values, and
     asserts the wrong error variant — it would not compile / would fail.

Fix

git rm the three orphaned files. No mounted module references them.

Verification

cargo check -p dsm is unchanged (the files were never part of the build).

CI gates & coverage

Full verification for this PR runs in CI — Rust (cargo fmt --check,
clippy -D warnings, workspace tests), Frontend, Android Unit Tests,
Coverage, SPDX headers, CodeQL (see the PR's Checks tab). The local
check noted above is a subset; the broader mandated gates (full workspace test
suite, codegen/scan, Android, Frontend) run in CI, not locally — none is
silently skipped.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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