fix(ship): agent-mode qa-verify no longer runs the host test suite; arch debate runs serial

[teragrid]

Problem

forge ship --agent-mode still hangs for many minutes with zero output on
1.10.4 — the mutex added in 1.10.4 stopped the arch-debate data race but not
the two contributors below. Observed dogfooding on ai-marketing-platfrom:
after answering an arch-parallel-debate turn, the next forge ship --agent-mode produced no output for ~15 min with the process alive.

1. qa-verify runs the caller's entire native test suite (main cause)

checkQAVerify Phase 2 calls runQATestSuite, which shells out to npm test
/ go test ./... / pytest on the host repo — with no agent-mode guard.
On a large project that's a multi-minute blocking run with its own stdout
stream. procspawn's timeout also doesn't reliably reap orphaned jest/vitest
workers on Windows: killing the parent npm/node leaves workers holding the
stdout pipe open, so the pipe read never sees EOF. When the pipeline reaches
qa-verify without pausing first — e.g. checkArch short-circuiting on an
already-present arch.md from an earlier answered turn — forge ship --agent-mode silently executes the caller's whole suite and appears hung.

In agent mode the host agent is the QA agent (the checkpoint's own
description: "QA agent: probe MCP server tools or run native test suite"), so
qa-verify now emits an advisory and lets the host run + report the suite.
Non-agent-mode runs are unchanged.

2. runParallelArchDebate still fans out against the bridge

The bridge can only surface one pending turn per run, so 5 of the 6 role
goroutines do throwaway work (redone on the next replay) while serialising
behind Bridge.mu as the first holds it across savePending's file I/O.
Agent mode now runs the debate sequentially, stopping at the first owed
turn — matching RunWithOptions's existing serial intent. The parallel
path is kept for real-provider runs.

Changes

File	Change
internal/cli/cmdship/ship.go	checkQAVerify Phase 2: skip runQATestSuite when pipe.Bridge() != nil; emit an advisory instead
internal/cli/cmdship/arch.go	runParallelArchDebate: sequential + early-exit when a bridge is active; parallel path retained otherwise
internal/cli/cmdship/rfc005_p1p2_test.go	New TestRunParallelArchDebate_AgentModeSerialNoFanOut — asserts no hang, one pending turn, coherent bridge state
CHANGELOG.md	[Unreleased] entries

Testing

• go test ./... — all green
• gofmt -l clean, go vet ./internal/cli/cmdship/... clean
• New regression test passes in 0.01s (vs. the hang it guards against)

🤖 Generated with Claude Code