ExpressionResolver::resolveMember iterates every receiver class

[Firehed]

Step 27 of docs/architecture/build-manifest.md.

Done

• no callsite in src/Resolution/ indexes [0] on getResolvableClassNames() — verified by disallowedMethodCalls in phpstan.neon (allowlist restricted to ExpressionResolver::receiverClassNames and SymbolResolver::getAccessibleMembers, plus the two Domain/ recursive-composition sites)
• hover, definition, and signature-help on \$x->onlyB() where \$x: A|B and only B declares onlyB answer the same way completion offers it — UnionReceiverParityTest
• a parity test asserts the four positional handlers and completion agree on union and intersection receivers — UnionReceiverParityTest covers Hover, Definition, SignatureHelp, Completion against the Entity|Person fixture where each constituent declares a distinct member; intersection agreement is exercised by the existing SymbolResolverTest::testGetMemberAccessContextForIntersectionParameterResolvesType
• the phpstan baseline for the rule reaches zero — the two step-27 entries in phpstan-baseline.neon are deleted; composer phpstan is clean

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.39%. Comparing base (d2d0dda) to head (dfa0b95).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #485   +/-   ##
=========================================
  Coverage     99.39%   99.39%           
- Complexity     1857     1864    +7     
=========================================
  Files           133      133           
  Lines          4780     4785    +5     
=========================================
+ Hits           4751     4756    +5     
  Misses           29       29           

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