Raise Coverage

Raise a package's coverage floor

Input: a package directory (for example packages/txpool) and optionally a target line-coverage percentage. Without a target, raise every threshold by five points or to what the new run measures, whichever is lower.

1. Run the package's coverage (vitest run --coverage in the package; never the bare test script, which is interactive). Read coverage/coverage-summary.json and list the files with the lowest line and branch coverage.
2. For each of the lowest files, read the implementation and write the missing cases in the colocated <name>.spec.ts. Tests use real objects: createTevmNode(), createMemoryClient(), real compiled contracts from @tevm/test-utils, recorded RPC snapshots. No vi.mock, no vi.fn on tevm objects (CLAUDE.md, testing conventions).
3. Cover error paths through the real error classes in @tevm/errors: assert on the error name and message, not on a mock being called.
4. Re-run coverage. Raise thresholds in the package's vitest.config.ts to the measured values rounded down to two decimals, and never above what the run measured. Do not touch autoUpdate.
5. Run the package's full test suite and its typecheck. Every test passes.

Do not change implementation files to make coverage easier. If a file is unreachable dead code, report it in your final message instead of testing it.