Fix cross-project deploy and add --remove-unmapped to project deploy

[midigofrank]

Short Description

Deploying a workspace to a different project sent none of its workflows. Cross-project deploys now send every local workflow, and a new --remove-unmapped flag deletes target workflows that don't exist locally.

Fixes OFN-4761, OFN-4762

Implementation Details

• Root cause: merge candidates came from findLocallyChangedWorkflows, which compares the workspace with its own forked_from. An unchanged workspace of A had no candidates, so deploying it to B sent B's workflows back unchanged (only a channel diff got past "Nothing to deploy"). This broke Lightning's GitHub -> OpenFn setup: green run, nothing deployed.
• When the target uuid differs from the local project's, deploy now takes the existing skipLocallyChangedCheck path: every local workflow is a candidate.
• --remove-unmapped (off by default): target workflows whose id isn't in the local project are sent as delete: true, and count as a change. Done in deploy rather than via Project.merge's removeUnmapped, which only omits workflows (Lightning rejects that) and would delete unchanged workflows under onlyUpdated.
• The divergence error now says when the target is a different project. --force is still required in that case.
• @openfn/project now exports Workflow.

QA Notes

• New deploy tests: unchanged A → B sends A's workflow and keeps B's; with --remove-unmapped B ends with only A's; same-project --remove-unmapped deletes a remote-only workflow; cross-project divergence message and --force. All fail before the fix.
• --remove-unmapped on a same-project deploy also deletes workflows created in Lightning since the last sync, without a divergence warning. That's what the flag means, but worth documenting.
• The printed plan doesn't list --remove-unmapped deletes (it diffs workspace vs remote, not the payload); --json-diff does.
• Will conflict trivially with the OFN-4760 PR in deploy.ts.
• Full-package ava runs segfault locally (also on the base commit); every test file passes individually.

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