feat: forward adapter-process stdio as debuggee output events — Ruby all platforms, Rust on Windows (#222, #223)

[debugmcpdev]

Summary

Closes the cluster:output-capture cluster: adapters whose debuggee inherits the adapter process's stdio now surface the program's output through get_output. Stacked on #253.

Two adapters have this topology:

• Ruby (Ruby: debuggee stdout/stderr is not captured (rdbg child stdio bypasses DAP output events) #222), all platforms: rdbg -c runs the target as a child of the adapter process; DAP travels over a separate TCP socket and the program's stdio lands on the adapter's pipes, which were drained into the proxy log only.
• Rust (Rust: launch config sets 'console' but CodeLLDB's option is 'terminal' — value likely ignored #223), Windows only: CodeLLDB's TerminalKind::Console performs no stdio redirection (launch.rs:460). On POSIX, LLDB holds the debuggee's pipes and CodeLLDB emits DAP output events from the STDOUT/STDERR process broadcasts (debug_session.rs:1478-1495); on Windows LLDB can't intercept, so the target inherits the adapter's handles. The channels are mutually exclusive, so the Windows-only opt-in cannot double-report on CI.

Mechanism

Mirrors the #247 worker-side synthesis pattern:

1. AdapterSpawnConfig's spawn variant gains an opt-in forwardStdio?: { excludeStderrLinePattern?: RegExp }. RubyAdapterPolicy sets it for launch — attach returns mode: 'connect' (no adapter process), so launch-only is enforced by construction — with a /^DEBUGGER: / exclusion for rdbg's stderr banners. RustAdapterPolicy sets it on win32 only. No other policy sets it → zero behavior change elsewhere (debugpy/js-debug adapter stdio is never forwarded).
2. GenericAdapterManager fans each stream's single LineBuffer out to the raw callback (all lines, blank included, unsanitized — the client must see the program's real output, parity with how debugpy/js-debug output reaches the buffer) while the persisted-log path keeps its blank-drop + sanitizeStderr redaction byte-for-byte.
3. DapProxyWorker synthesizes sendDapEvent('output', { category, output }), so entries land in the existing per-session ring buffer with no changes above the proxy.

The exit-flush race (found in live verification, not in planning)

A debuggee printing to a block-buffered pipe (Ruby's default) flushes everything at exit — milliseconds after the adapter's terminated event and DAP socket close. The SessionManager reacts to either signal by stripping listeners and stopping the proxy, so the first live run captured the stderr marker but lost all 15 stdout lines. When forwarding is active, the worker now holds exited/terminated forwarding and the dap_connection_closed status behind a stdio-drain barrier (both streams' close events, 2 s backstop). Stream data fires before close and IPC is FIFO, so the flushed output deterministically reaches the buffer first. A worker unit test pins the ordering.

Verified live (Windows, dev proxy)

• Ruby fizzbuzz: all 15 puts lines as stdout (including the exit flush), warn marker as stderr, zero DEBUGGER: entries.
• Rust hello_world: complete program output as stdout, including the post-Process exited tail.
• Ruby attach regression: e2e attach smoke test passes unchanged.

While verifying, found a pre-existing Windows CodeLLDB quirk (unrelated to this change): continue_execution from a breakpoint re-stops at the same breakpoint — filed separately. The Rust e2e output assertion is designed around it (both markers print before the breakpoint, no continue needed).

Test plan

• tests/unit/proxy/dap-proxy-adapter-manager.test.ts — fan-out: raw callback + redacted log copy (the load-bearing parity assertion), blank lines, chunk-straddle, single flush on end+close, no-callback unchanged
• tests/proxy/dap-proxy-worker.test.ts — Ruby launch wires the forwarder (banner exclusion, blank → "\n"); Python gets none; drain barrier holds terminated/dap_connection_closed until streams close, output ordered first
• tests/adapters/ruby/unit/adapter-policy-ruby.test.ts + packages/shared/tests/unit/adapter-policy-rust.test.ts — opt-in shape, banner pattern semantics, win32-only gating
• tests/e2e/mcp-server-smoke-ruby.test.ts — asserts 6: Fizz (stdout), fizzbuzz complete (stderr), no DEBUGGER: entries
• tests/e2e/mcp-server-smoke-rust.test.ts — asserts both hello_world markers as stdout
• tests/e2e/mcp-server-smoke-ruby-attach.test.ts — attach unchanged
• Full unit tier: 159 files / 2627 tests green; lint clean

Fixes #222. Fixes #223.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 97.91667% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/proxy/dap-proxy-worker.ts	97.14%	1 Missing ⚠️

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