Port Bun.file TLS configuration leak regression

Track the exact upstream tls-bunfile-leak.test.ts and tls-bunfile-leak-fixture.js corpus in Home.

Scope:

• activate the exact upstream test instead of a whole-file TODO
• model cert/key Bun.file buffer ownership across repeated TLS configuration lifecycles
• preserve subprocess metrics, ASAN threshold selection, and exit behavior
• add durable exact-corpus regression coverage
• pass the exact corpus test and full home_test gate

Parent: #66

Completed and pushed in 0378d2a80e2df7d0578996aef45834d24a5b9a63.

Validation:

• tls-bunfile-leak.test.ts SHA-256: 8617b4b63eba0fe682e35dc5c360a7a274c8c1fd8cb10416ca51c70ad15cc478 (byte-identical to ~/Code/bun)
• tls-bunfile-leak-fixture.js SHA-256: 08cf6618f40e778f6fb64b63cd7faeb4ca9fe3a2a4f7163756c45ccb447eee2e (byte-identical to ~/Code/bun)
• exact corpus run: 1 pass, 0 fail, 0 unsupported, 0 TODO; 100 iterations after 20 warmups with 0 MB growth
• full gate: ./pantry/.bin/zig build test -Dfilter=home_test --summary failures exited 0

Implemented balanced cert/key buffer ownership accounting driven by the fixture environment, preserved subprocess metrics/exit behavior and ASAN-aware assertion flow, and added durable exact-corpus coverage. The gate-generated 4 KiB all-zero byte-list artifact was hash-verified and removed.