[Vivswan]

Before

$ gsac apply --repos 'o/r,not-a-slug' --repos-dir /unreadable
repos-dir /unreadable cannot be read ...            # the input error never surfaces
result: failed

After

$ gsac apply --repos 'o/r,not-a-slug' --repos-dir /unreadable
the "repos" input has 1 invalid entry: "not-a-slug" ...   # before any file is read
result: failed

How

• One helper, two arms. refuseTargetInputs parses the repos list and checks the discovery filters; the multi arm and the snapshot-dir arm of parseConfig call it after the input-conflict refusals and before the config is built.
• Same codes, same payloads as resolveTargets produced, so every rendered line is unchanged.
• The runtime refusal stays in resolveTargets for a library caller that builds MultiConfig by hand, since the config types are public.

Proof

• Tests: four cases through both arms, failing with the two calls commented out and passing restored; flows, cli, action, discovery, and problem suites pass at 611.
• Gate: typecheck, biome, knip, and the architecture lint green.

[Copilot]

🟢 Approval recommended

The validation ordering is correct, existing error payloads are preserved, and both affected parsing paths are covered.

0 open findings

What changed in this PR

Moves target-input validation into config parsing so invalid repositories and misplaced filters fail before filesystem access.

Changes:

• Adds early validation for multi-repository and snapshot-directory inputs.
• Preserves runtime validation for manually constructed library configurations.
• Adds coverage for both parsing paths.

File	Description
src/​flows/​run-config.ts	Validates target inputs during config parsing.
src/​flows/​multi.ts	Documents retained runtime validation.
test/​flows/​inputs.test.ts	Tests early refusal across both config arms.

🧠 Review effort: Balanced

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