Microflow create or modify as diff-then-patch: an unchanged definition writes nothing (4.2g, beta gate)

[ako]

Plan item 4.2g in the proposal (§8.3 point 4, ADR-0012 decision 3). On the beta gate.

Today create or modify microflow rebuilds the whole document, and canon/transplant.go re-pairs IDs by type and position. The round-trip test's #721 class A (curves reset, merges dropped, IDs moved) comes from this.

Scope:

• Match the declared flow against the stored one by statement signature and output variable, using the alter microflow: content-addressed target resolver (output variable, caption, statement pattern) #713 resolver.
• Derive the minimal insert, replace and drop operations.
• Apply them with the alter microflow/nanoflow: graph splice, placement, insert/replace/drop (#736) #739 splice engine.
• An unchanged definition must produce an empty patch and no write.

Done when:

• The round-trip test's microflow and nanoflow entries in Round-trip harness: untracked describe → exec losses on the Studio Pro fixture (microflows, entities, pages, snippets, menus, roles, JS actions) #721 class A are struck.
• On a Studio Pro-authored flow, an unchanged describe → create or modify is byte-identical, with an edited-flow control that does write.

Tracking: #714. Language rules: ADR-0010/0011/0012. Changes of meaning apply only under the mdl 1 header; old spellings stay as registered deprecated aliases, each with an fmt --upgrade rewrite (#742).