[kddejong]

Issue #, if available:

Description of changes:

CreationPolicy and UpdatePolicy must resolve to an object. CloudFormation
rejects a bare intrinsic standing in for the whole object with
Template format error: Expected an object (verified against live
CloudFormation). Only an object literal or Fn::If (which resolves to an
object) is valid there; Ref/Fn::Sub/Fn::FindInMap, and Ref to a
resource or pseudo parameter, are not. Intrinsics nested at leaf properties
(e.g. ResourceSignal.Count: !Ref Count) remain valid.

Previously these were missed: E3055/E3016 allowed the full function set and
leaned on type inference, and UpdatePolicy errors were swallowed entirely.

Changes

• allOf no longer flips unresolvable_function_mode or rolls errors up into a
  single "Cannot determine allOf". allOf is conjunctive — every subschema
  must hold and there is no branch to select — so an unresolvable intrinsic
  creates no ambiguity there; the suppression only hid legitimate errors. That
  mode still applies to the disjunctive keywords (anyOf/oneOf/if). This
  lets UpdatePolicy (E3016), whose schema is expressed via allOf/if/then,
  surface these errors the way CreationPolicy (E3055) already does.
• E3055/E3016 validate against plain object schemas and blank Resources from
  the reference context, so Ref to a resource is caught.
• Ref (E1020) now resolves pseudo-parameter types (string, or list for
  AWS::NotificationARNs) and validates them against the schema, mirroring the
  existing named-parameter check, so Ref to a pseudo at an object slot is
  caught.
• Added integration templates and snapshots for CreationPolicy and
  UpdatePolicy (test/fixtures/templates/integration/,
  test/fixtures/results/integration/).

Verified against live CloudFormation (CreateStack):

Value at the policy slot	CloudFormation
object literal	accepted
Fn::If (object branches)	accepted
Ref (param / resource / pseudo), Fn::Sub, Fn::FindInMap	Expected an object
Ref: AWS::NoValue	Expected an object
nested leaf intrinsic (Count: !Ref P)	accepted

Known follow-up: Fn::Select is not yet rejected at the object slot
because its declared output type is all_types (it can legitimately resolve to
an object via a list of objects, e.g. through Fn::FindInMap). Tracked
separately.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.61%. Comparing base (d8d5bfb) to head (ea6590b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4641      +/-   ##
==========================================
+ Coverage   94.58%   94.61%   +0.02%     
==========================================
  Files         432      432              
  Lines       15417    15426       +9     
  Branches     2986     2991       +5     
==========================================
+ Hits        14582    14595      +13     
+ Misses        456      453       -3     
+ Partials      379      378       -1     

Flag	Coverage Δ
unittests	94.61% <100.00%> (+0.02%)	⬆️

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