fix(scaffold-create): auto-cleanup downloaded scaffold after create (#157)

[ericelliott]

Problem

Running npx aidd create <url> a second time failed with a destination-conflict error because ~/.aidd/scaffold/ was left on disk. The previous code returned a cleanupTip hint but never ran cleanup automatically.

Additionally, there was an asymmetry in the public CLI: no way to opt out of cleanup (no --keep flag), yet scaffold-cleanup existed as a public subcommand.

Fixes #157.

Solution

Commit 1 — auto-cleanup on success

runCreate now automatically calls scaffoldCleanup() after a successful runManifest when paths.downloaded === true. Named and file:// sources are unaffected.

Commit 2 — move cleanup to finally; remove public subcommand

• Cleanup is now in a try/finally block so it fires on both success and failure (e.g. a manifest step throws). This eliminates the last scenario where ~/.aidd/scaffold/ could be orphaned.
• scaffold-cleanup subcommand removed from the CLI. With no --keep flag, a public cleanup command is pointless and confusing. scaffoldCleanup remains an internal function.
• scaffold-resolver.js error message updated to say "delete manually" instead of "run npx aidd scaffold-cleanup".

Changed files

File	Change
lib/scaffold-create.js	scaffoldCleanupFn in try/finally; updated JSDoc
lib/scaffold-commands.js	Removed scaffold-cleanup subcommand and its import
lib/scaffold-resolver.js	Updated destination-conflict error message
lib/scaffold-create.test.js	Added tests: cleanup-on-success, cleanup-on-failure, no cleanup for non-downloaded
lib/scaffold-commands.test.js	Removed scaffold-cleanup from expected command list; dropped its vi.mock
lib/scaffold-resolver.test.js	Updated mentionsCleanup → mentionsDelete assertion
bin/create-e2e.test.js	Removed aidd scaffold-cleanup describe block; updated success-message test
docs/scaffold-authoring.md	Documented automatic cleanup behaviour
tasks/npx-aidd-create-epic.md	Updated requirements
tasks/scaffold-review-followups-epic.md	Updated error-message requirement
plan.md	Updated task count

Tests

• 349 unit tests pass (+1 new test for cleanup-on-failure)
• 45 e2e tests pass
• Lint and type-check clean