Add meaningful verification to liberty ECSM, sky130 corners, writer,
and roundtrip tests. Expand verilog specify, escaped-write, remove-cells,
write, and writer tests with content checks, roundtrip validation, and
error guards. Update corresponding .ok golden files.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Jaehyun Kim <jhkim@precisioninno.com>