Wire operators and operator_axis options in provider (#8, #54)

[jc-macdonald]

Summary

Expose operator metadata through SystemABC.option() so downstream engines (e.g., op_engine) can discover IMEX operator configuration without re-parsing the spec. Also fixes a bug where whitespace in template equation keys caused false validation errors.

Changes

Bug fix — specs.py whitespace normalisation (01cbe8e)

Equation keys written with spaces inside brackets (e.g., "u[x, y]") failed validation because _expand_state_templates builds canonical keys without spaces ("u[x,y]"). Added _normalize_bracket_key to strip whitespace inside brackets at equation-map entry, using the existing _STATE_TEMPLATE_RE regex. Tested with 2-axis and 3-axis cases.

This helper is intentionally minimal — broader parsing consolidation is tracked in #30 and the Pydantic-ify milestone (#22, #28).

Feature — operator wiring (4a3bef5)

Two new static methods on OpSystemSystem:

• _extract_operators → returns tuple[MappingProxyType, ...] | None from compiled.meta["operators"]
• _extract_operator_axis → returns the shared axis name (str) when all operators act on one axis, otherwise None

Wired into model_post_init alongside the existing mixing_kernels:

self.options = {
    "mixing_kernels": mixing_kernels,
    "operators": operators,
    "operator_axis": operator_axis,
}

Operator dicts are stored as MappingProxyType to prevent callers from accidentally mutating spec metadata.

Tests added

• Equation key spaces accepted (2-axis and 3-axis)
• Extra whitespace around axis names normalised
• Operators present/absent via option()
• Immutability enforcement (MappingProxyType rejects mutation)
• Single vs. mixed operator axis detection
• Multi-operator specs surface both operators
• Operators independent of mixing_kernels

Closes

• Closes Add op_engine compatible operator wiring #8
• Closes Wire operators and operator_axis options in provider #54

Related

• Revisit helper logic #30 (revisit helper logic) — _normalize_bracket_key will be absorbed when parsing is consolidated
• Add ExpressionString type #22, Add Operator Pydantic model #28 (Pydantic-ify milestone) — structured models will replace ad-hoc dict parsing
• op_system flepimop2 adapter upgrade #12 (adapter upgrade) — separate PR

[pearsonca]

LGTM