Module exchange_lookup 

Exchange-scoped lookup path grammar shared by SQL :# placeholders and Simple ${...} interpolation. See ADR-0016 (strict rejection) and the rc-o6o Phase 2 spec §3.2.

Grammar (e_gpt decision Q2):

• body.a.b.c → Body([Key("a"), Key("b"), Key("c")]) — walks JSON.
• body.items.0 → Body([Key("items"), Index(0)]) — array index.
• header.some.name → Header("some.name") — flat key.
• property.x → Property("x") — flat key.
• exchangeProperty.x→ Property("x") — alias.
• foo → Unscoped("foo") — try body JSON key, then header, then property.

Enums

ExchangeLookupPath

A parsed Exchange lookup path. See module docs for the grammar.

LookupPathError

Error raised by ExchangeLookupPath::parse. Aligns with ADR-0016 strict rejection: ambiguous / malformed paths are reported, never silently coerced.

PathSegment

A single segment in a body JSON path.