fix(workforce-validation): bind PostgreSQL connection capability from tuple storage

[seonghobae]

Finding

PostgresValidityStudyReadPort stores its accepted connection_factory in tuple-backed storage, but predecessor read_validity_study(...) invoked it through self.connection_factory(). A subclass could override that property (or dynamic attribute resolution) and substitute a different executable connection capability after construction, defeating the structural-binding guarantee introduced by #250.

This is a checked-versus-used dependency boundary: the constructor validated/stored one callable, while the executable read could resolve another callable later.

Test-first repair

• ceb72ff997fdf54640a146c8569b0ee225312507: focused regression creates a PostgresValidityStudyReadPort subclass whose connection_factory property returns a replacement callable. The inherited read must still call only the original constructor-accepted factory.
• d54d44d795444df572efbb301a667d74ac574d58: production reads the executable dependency directly from base tuple storage with tuple.__getitem__(self, 0) and invokes that local callable. The public property uses the same direct tuple read.
• Compare from fix(workforce-validation): preserve validity-study case trigger after registry adoption #251 head b210b6bd201a9b62949da33bc4a9feb92ec6a095 is two ordinary commits ahead / zero behind and changes only the PostgreSQL adapter plus the focused regression.

CodeRabbit independently reviewed exact d54d44d795444df572efbb301a667d74ac574d58 and reported no defect in the requested #252 scope. It confirmed the test-first predecessor, direct tuple-storage selection, UUID snapshot ordering, read-only transaction, tenant-local set_config, schema-qualified parameterized owner SQL, bounded fetch, row reconstruction and absence of unrelated parent-owned changes. This is static evidence only; it did not execute tests/PostgreSQL/coverage and is not a qualifying approval or hosted GREEN.

Acceptance still open

• Preserve UUID pre-connection snapshots, read-only transaction scope, tenant-local RLS context, schema-qualified owner SQL, bounded fetch, exact row reconstruction, and fix(workforce-validation): make PostgreSQL read-port dependency structurally immutable #250 retained-reference immutability.
• Do not copy mutable feat(workforce-validation): establish governed validity-study registry boundary #235 source or alter parent-owned application authorization code.
• After feat(workforce-validation): establish governed validity-study registry boundary #235 integrates normally, feat(workforce-validation): adopt registry into owner persistence #248 must non-force adopt protected parent truth/retarget to develop, preserve fix(workforce-validation): bind PostgreSQL connection capability from tuple storage #252, and reacquire fresh exact-head Foundation/PostgreSQL/security/review evidence.

Keep #252 open until that protected integration. Source repair or static review alone is not a close condition.