guard: fix the perpetually-failing go list guards at the source

[timothyerwin]

The failure

TestVendorSDKsOnlyInTheirAdapters and TestNoGatewayInternalsOutsideGateway have been failing on every branch, generally blamed on desktop/node_modules. That was the trigger, not the cause.

go list exits 0 and returns a complete, correct package list — the symlink lines are advisory warnings on stderr. The guard helpers used CombinedOutput(), which folded those warning lines into the package list. Each one was then handed back to go list as a package path, and .../node_modules@electron/... contains an @, which in module-aware mode reads as path@version and is only valid for go get/go install. That invocation exited 1.

The bug was the helper laundering stderr into data.

The fix

One goListLines helper reading stdout only, used by deps, directImports, and modulePackages. Any go list warning is now inert whatever its cause — an untracked node_modules tree from another branch (desktop/ isn't tracked on main at all), a stray symlink, anything future.

Genuine failures still fail: non-zero exit is fatal, and an empty package list is now explicitly fatal too — that would otherwise let every guard below pass vacuously, which is the failure mode this class of test is least able to notice.

Verified

• Full go test ./... green with desktop/node_modules still in place.
• Guards still have teeth: injecting an anthropic-sdk-go import into internal/wire correctly fails TestWireIsStdlibOnly.

Also repairs two comments still pointing at docs/design/personal-agents.md, renamed to autonomous-agents.md during the consolidation.