feat: improve live edit Link renames and previews

[tbrandenburg]

Summary

• Allow revision-safe name-only edits for existing Link In, Link Out, and Link Call nodes.
• Report changed flow objects separately from flow-order metadata in preview summaries and additive JSON counts.
• Document the serve → edit → run user-directory roundtrip.

Closes #80
Closes #81
Closes #82

Validation

• make ci — formatting and lint passed; 179 tests passed. The best-effort npm audit reports 5 transitive advisories (2 moderate, 3 high); the Makefile intentionally ignores audit failure.
• node --test --test-concurrency=1 test/unit/edit.unit.test.js test/integration/edit-acceptance.integration.test.js — 28 passed.
• Real Node-RED acceptance coverage: Link preview/apply/rejected edits/restart persistence; change-count human/JSON preview and no-deploy checks; serve/edit/apply/run roundtrip with shared userDir on free alternate port 1883, including output 9.
• CLI help checked for serve, edit, edit preview, and run.

Review and risks

• Adversarial review found no actionable findings.
• No code-level follow-up known; existing dependency audit advisories are unrelated to this change.