fix(cli): doctor reports "healthy" on a project that was never set up

[blafourcade]

Problem

On a project with no manifest, aidd doctor prints three Warning: [scope] No AIDD manifest found... lines, then still prints "Installation is healthy" and exits 0.

Root cause

src/application/use-cases/global/doctor-all-use-case.ts:47-55's computeHealthy treats each errored (null) scope report as vacuously healthy: ai === null || ai.healthy.

Evidence

Verified on an empty directory:

$ node dist/cli.js doctor
Warning: [ai] No AIDD manifest found...
Warning: [ide] No AIDD manifest found...
Warning: [plugins] No AIDD manifest found...
✔ Installation is healthy

Exit code 0.

Why it matters

A CI gate like aidd doctor && deploy passes green on a project that was never initialized — the exact failure mode doctor exists to catch.

Fix

Either make doctor report unhealthy (non-zero exit) when any scope errored, or drop the "healthy" success line entirely when errors.length > 0 and print a neutral "nothing to check, run aidd setup first" message instead.

Acceptance criteria

• aidd doctor on an uninitialized project does not print "Installation is healthy"
• Exit code reflects the actual state (non-zero, or a distinct "not set up" signal)

Found by a UI/terminal-UX audit of cli/ — full report: cli/aidd_docs/tasks/2026_07/2026_07_22_audit/ui.md.