feat: ignore unresolved import patterns

[longlho]

Summary

• Fold unresolved import ignore patterns into the unresolvedImports config object.
• Remove the separate ignoreUnresolved top-level option.
• Keep mode and ignored unresolved specifier patterns in one config surface.

Example

{
  "unresolvedImports": {
    "mode": "report",
    "ignore": ["#virtual_generated/**"]
  }
}

Test plan

• cargo fmt --check
• git diff --check
• cargo test --workspace
• bazel test --test_output=errors //tests/fixtures/runfiles-fixture:codescythe_runfiles_test //tests/fixtures/runfiles-false-positive:codescythe_false_positive_test