fix: v1.8.1 — --dry-run no longer mutates on activate/deactivate

[trngthnh369]

The bug

workflow activate and workflow deactivate ignored --dry-run and performed the
change anyway. All 25 other mutation verbs guard on the flag, so a caller reasonably
treats --dry-run as a safe way to see what a script would touch on production:

$ n8nctl workflow --dry-run deactivate <id>
○ deactivated workflow <id> "Sub: Content Generator"     # ← it actually did it

A --dry-run that mutates is doing the opposite of its contract, and this is the more
damaging half: it takes a live workflow offline.

How it surfaced

Running that exact command against the live instance while verifying the 1.8.0
release — it printed deactivated where [dry-run] was expected. No damage: the
target was already inactive and updatedAt never moved (still 2026-05-13), confirmed
before and after.

It is pre-existing, not introduced by 1.7.0/1.8.0. It was raised as a LOW
"out-of-scope" note during the #3 review and deprioritised there — which in hindsight
undersold it, since the flag's entire purpose is production safety.

The fix

Both handlers now GET the workflow, print a [dry-run] preview, and issue no write:

$ n8nctl workflow --dry-run deactivate <id>
[dry-run] would deactivate workflow <id> "Sub: Content Generator" (already inactive — no change)

The preview flags a no-op so a dry run doesn't imply a change that wouldn't happen, and
is machine-readable under --json ("dryRun": true, "alreadyInactive": …).

Tests

The regression tests assert the POST is never issued, not just the wording — a
--dry-run bug is exactly what a passing "it printed something" test would miss:

env.apiMock.onPost('/workflows/42/deactivate').reply(() => { posted = true; … });
await deactivateHandler(env.factory, {}, ['42']);
expect(posted).toBe(false);

516 tests (+5), coverage gate green, lint/build/audit clean. Re-verified against the
live instance: updatedAt unchanged after the fix.

Not tagged — v1.8.1 is bumped in package.json + CHANGELOG.md.

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