@fix formal specification: stratified fixpoint computation over typed reasoning graphs

Complete spec for FlowScript's fixpoint combinator — the operator that transitions
FlowScript from representation language to computational language.

Covers: semantics (L0/L1/L2 constraint levels), syntax (EBNF + examples), IR
extensions (fixpoint node type, fixpoint_derived relationships), termination proofs
(Knaster-Tarski, Gurevich-Shelah, Immerman-Vardi), convergence semantics
(content-hash dedup = semi-naive evaluation), audit trail interaction (Curry-Howard:
L1 audit trail IS constructive proof), linter rules (E007-E009), query interaction.

Formal foundations: SQL precedent is exact (not analogy). No other system stratifies
computational power across shared notation by design. First intentional implementation
of decidable compliance + Turing-complete cognition in same notation.

Draft v1.0 — integration into existing spec files (grammar.md, semantics.md,
ir.schema.json, linter-rules.md, critical_queries_spec.md, golden_examples_spec.md)
planned as follow-up.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: phillipclapham