Track implementation: formula-as-EDGE (field formulas)

[chouswei]

Summary

Track implementation of the formula-as-EDGE design: derived numerics modelled as durable EDGE relations (e.g. rel=derives / formula), with field locators on the edge payload, not inline expression syntax on NODE fields. Write = display; pin map shows absolute field values plus the relation line.

Design SSOT: docs/grammar/memnet-field-formulas.md

Design landed in docs: 959f124 — Document field formulas as EDGE relations (derives/feeds).

Scope (implementation, not yet in engine)

• Same-node self-loop formula edges as the first dialect candidate
• Bare-present EDGE lines on pin map; target values remain absolute numbers
• Materialise target on write when an expression engine exists (evaluation policy); no expression engine in 0.3.6+ per design
• Keep locked +=/-= literal-only; do not overload LAW or add CALC as a third kind

Out of scope for this tracker (unless design changes)

• Primary authoring via cashflow:=rent-expenses node sugar (may compile to EDGE later)
• Full cross-node expression language

Acceptance (draft)

• Wire/mutate accepts documented formula EDGE shape(s)
• Pin map renders formula edges in shared dialect
• Optional: re-materialise derived fields after source +=/-= updates (when engine exists)
• Tests and grammar doc cross-links stay aligned with memnet-grammar-design.md

[chouswei]

Clarification: two layers (do not conflate)

1. Generic formula grammar — `docs/grammar/memnet-field-formulas.md`: formula-as-EDGE (`derives`/`feeds`, multi `src_fields`, `tgt_field`, `expr`) for any domain. This issue tracks that design / future engine.
2. Nodal circuitry application — `docs/application-notes/llm-nodal-analysis-formulas.md`: express a circuit with the node method (NET/CMP/PIN, KCL/Ohm stamps, absolute V/I). It uses (1); it does not define the formula grammar.

Docs updated to lead each file with its layer and cross-link the other.

[chouswei]

Backlog priority (0.4.x): Remains design + future engine per docs/grammar/memnet-field-formulas.md. Explicitly lower priority than MN-REQ-12.7 deferred items (ACL #28, reserve #30, ingest #31, WorkerWriteScope #32) in docs/multi-agent-sessions.md / CHANGELOG.md Unreleased. No change to acceptance checklist until an expression/materialisation engine is in scope.