Adds OptsGoParityTests.cs with 49 tests porting 15 unmapped Go test
functions from server/opts_test.go: random port semantics, listen port
config variants, multiple users, authorization block parsing, options
defaults (TestDefaultSentinel), write_deadline parsing, path handling,
variable/env-var substitution chains, and unknown field tolerance.
test_parity.db contains go_tests (2,937 rows) and dotnet_tests
(2,966 rows) tables for querying Go-to-.NET test mapping across
Claude sessions. 857 mapped, 2,080 unmapped.
