devlore-test run fails on Windows: output streams default to /dev/stdout #379

devlore-test run cannot execute on Windows. Its default output routing names Unix device paths, which do not exist there, so the command fails before producing any output.

Mechanism

cmd/devlore-test/devloretest/commands.go:53-55 sets the default for every stream:

"summary": "/dev/stdout",
"receipt": "/dev/stdout",
"graph":   "/dev/stdout",

On Windows the open fails and the command aborts:

error: opening graph output: open /dev/null: The system cannot find the path specified.

/dev/null appears the same way in the documented examples at commands.go:71, commands.go:73, commands.go:78, and root.go:43, root.go:45, so the guidance shipped to users is also Unix-only. Ten references in production code, nineteen more across tests, and one Starlark fixture (data/test_compensation.star).

Evidence

From the second three-platform CI run (PR #378, commit 762c61ec, job test (windows-latest)). After the .exe fix let the binary start, the CLI now runs and exits 1 with empty stdout for every test that executes a script:

--- FAIL: TestCLI_ScriptFirst
    cli_test.go:137: exit code = 1, want 0
    cli_test.go:138: no JSON summary found in output
--- FAIL: TestCLI_DefaultAllToStdout
    cli_test.go:157: exit code = 1, want 0
    cli_test.go:158: output missing "Hello World!" (len=0)

Roughly 16 of the 47 remaining Windows failures trace to this one default — the 12 exit code = 1 cases, the 5 "no JSON summary" assertions, the 2 "missing Hello World!" assertions, and the 2 explicit /dev/null failures in commands_test.go.

It was invisible until now for two reasons: CI ran the unit suite on ubuntu only (#373), and until the .exe fix the binary never started on Windows at all, so this failure sat behind that one.

Why it is a product defect rather than a test problem

The default is in the shipped command definition, not in a test. Any Windows user running devlore-test run test.star hits it immediately, with no flag combination in the documented examples that avoids it — the examples themselves route to /dev/null.

Likely shape of the fix

The three streams want a platform-neutral way to say "standard output" and "discard" — a sentinel the routing layer resolves (os.Stdout, io.Discard) rather than a filesystem path handed to open. os.DevNull is Go's portable constant for the discard case and is NUL on Windows. Whether the sentinel should remain spelled /dev/stdout for continuity, or become something explicit like - or stdout, is a surface decision worth making deliberately, since it appears in help text, examples, docs, and at least one Starlark fixture.

Found by the platform test matrix (#373). Classified bucket 1 — a genuine platform defect — under that plan's phase 2 triage.