fix(#492): don't park ruby launches on an initialize response rdbg never sends

[debugmcpdev]

Summary

rdbg can process the initialize request — provably, since it emits the initialized event 34ms later — yet never write the response frame. The worker awaited that response unconditionally (dap-proxy-worker.ts initialize step), so the launch sat silent until the parent's 30s deadline killed the session blaming adapter startup, even though an immediate retry always worked (3 occurrences across the last 48-combo sweep; full evidence in #492).

The fix

• New InitializationBehavior.initializeResponseOptional flag, declared only by RubyAdapterPolicy — launch mode only, attach keeps the strict await (ruby attach shares the policy, so the worker guard also excludes attach explicitly).
• Worker: awaitInitializeResponse() races the response against the already-armed initialized event plus a 2s grace period (matching the existing Phase-1 wait convention). Event wins ⇒ warn naming exactly what happened (greppable, references Ruby/rdbg: 30s proxy-init timeout recurs after #470 — initialize response never arrives, with no framing error this time #492) and proceed with capabilities = undefined — a documented-legal value every consumer already guards. A late response still captures capabilities; its eventual timeout rejection is swallowed so it can't become an unhandled rejection. The grace timer is cleared when the response wins — no stray timers.
• Removed the istanbul ignore on the launch-before-config branch — the new tests exercise it.

Why proceeding is safe

The DAP spec makes initialized strictly follow successful initialize processing, so the event is proof the request was served; a dropped response will never arrive (DAP has no resend). Nothing downstream hard-requires capabilities: the worker's config sequence derives from policy, and every parent consumer guards absence (supportsExceptionInfoRequest?., logpoint downgrade check, mirror ?? undefined).

Residual: an rdbg wedged for all responses (launch too) still hits the 30s deadline — that case is what #493's diagnostics (next PR) will name honestly.

Tests

• Red-then-green regression: ruby launch + never-resolving initializeSession + fired initialized ⇒ launch/configurationDone proceed, warn logged, no capabilities status (timed out before the fix).
• Late response after the event won ⇒ capabilities still captured.
• Healthy ruby launch unchanged (response wins the race; no warn).
• Gating: go (no flag) and ruby attach still block — pinned.
• Live: against a response-dropping fake rdbg, start_debugging completes in ~4s (2s = grace) with the recovery warn in the proxy log, instead of failing at 30s with the misleading message.

Fixes #492

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 96.29630% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/proxy/dap-proxy-worker.ts	96.29%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!