Predicate scope — the frozen assert/cel field table (ADR-0013 consequences)

This table is the closed set of top-level fields a CEL leaf inside assert/when (ADR-0013) may reference. It exists so MergePolicy's assert/cel leaves have one authoritative field list, referenced by name from schemas/policy/v1alpha1/merge-policy.schema.json, that a future assent lint implementation checks unknown-field references against (ADR-0016 §2: unknown fields are load-time errors, never <no value>). Adding a field here is a schema-fixture-gated change, not a drive-by edit — REQ-P3-E1-S06-01 lists "undeclared predicate-scope fields" as a lint hard error precisely to keep this table authoritative.

Field	Meaning	Source type	Scope
old	Pre-change value at the matched pointer	value (same shape as the pointer's target)	change
new	Post-change value at the matched pointer	value (same shape as the pointer's target)	change
path	The matched pointer/path itself	string	change
kind	The matched change's lifecycle kind	add \| modify \| delete \| rename	change
file	Repo-relative path of the file the matched change lives in	string	change
entry	Head-state value tree of the containing EntryRef	value tree (shape of the governed entry)	change
oldEntry	Base-state value tree of the containing EntryRef (absent for add)	value tree, nullable	change
changes	All changes in this class slice (the whole matched set, not just the current one)	array of Change	change
facts	Provider results, keyed by provider name then output name (ADR-0004)	map of typed fact values	change + mr
mr	MR/PR metadata: author, branches, labels	object	change + mr
env	Environment label from the classifier (ADR-0008)	string	change + mr

Naming precedent: Kubernetes ValidatingAdmissionPolicy's object/oldObject (entry/ oldEntry here play the same role, scoped to one governed EntryRef rather than the whole admission object).

Rules

• This is the entire set. No other top-level identifier may appear in a CEL leaf; a reference to anything else is an assent lint hard error (docs/planning/lint-hard-errors.md), never a silent <no value> or a runtime CEL "no such attribute" surprise.
• facts.<provider>.<output> and mr.<field> are the only two fields with a further-nested, provider/forge-defined shape; every other field's shape is fixed by the schemas in this epic (EntryRef, Change, the four matcher-domain shapes).
• Adding a field to this table requires a schema-fixture change (a new positive fixture that exercises it) — this table and merge-policy.schema.json's assert/cel description stay in lockstep by construction, not by convention.

Source

Carried over verbatim in substance from ADR-0013 appendix, "Predicate scope", frozen here as the companion contract ADR-0013's consequences promised ("Predicate scope becomes contract... Freezes with fixtures in Phase 3").