Problem

While validating draft PR #3997 against a real, large Studio site before SQLite-to-MySQL conversion, the supported full-site export command exited successfully with no diagnostic but produced an invalid archive.

Reproduction

Integration build: current origin/trunk plus PR #3997, commit 3e547db03 in a managed test worktree.

node apps/cli/dist/cli/main.mjs export 
  /Users/.../intelligence-chubes4-full.zip 
  --path /Users/.../intelligence-chubes4 
  --mode full

Source SQLite database size: 19,880,640,512 bytes.
Produced archive size: 8,440 bytes.

Validation:

End-of-central-directory signature not found
unzip: cannot find zipfile directory

The command returned success and printed no warning/error. The source site remained unchanged.

Expected

A successful export produces a readable full-site archive. Any interrupted, unsupported, capacity-limited, or failed export exits non-zero, removes/marks the partial artifact, and reports the failing phase with actionable diagnostics.

Why this matters for #3997

studio convert --to mysql is intentionally being validated first against a clone with a verified rollback artifact. Silent export corruption makes the documented safe migration path appear ready when no usable rollback exists.

Acceptance criteria

• Large SQLite full exports produce a valid archive or fail non-zero.
• Partial archives are never reported as successful.
• Export performs a final archive-integrity check before success.
• Regression coverage includes an interrupted/failed archive stream and bounded large-file behavior.

AI assistance

• AI assistance: Yes
• Tool(s): OpenAI GPT-5.6 Sol via OpenCode
• Used for: Integrating Add MySQL proof of concept #3997 with current trunk, running the migration preflight, and capturing deterministic export evidence.