[VEF Hook]: Query lifecycle hooks

[villagesql-adam]

Production-grade hooks covering the full query lifecycle: parse, optimize, execute, and teardown. Enables extensions to observe, annotate, or intercept queries at each phase without modifying server internals.

Required by

Epic	Issue
[Epic] Multi-Tenant Row Isolation	#329
[Epic] Database Observability Pipeline	#331

[villagesql-adam]

Related lifecycle / interception issues for cross-reference:

• [VEF Hook]: Statement execution notification #607 Statement execution notification (post-exec observation, phase E)
• [VEF Hook]: Statement completion events #617 Statement completion events
• [VEF Hook]: DDL pre-execution interception #272 DDL pre-execution interception
• [VEF Hook]: Query interception infrastructure #261 Query interception infrastructure
• [VEF Hook]: Query result interception #289 Query result interception
• [VEF Hook]: Row-level security enforcement #315 Row-level security enforcement (predicate injection)
• vef: Add Statement Events Capability #645 PR — phase E (post-execution, read-only) lands first

PR #645 implements one slice (post-execution, read-only) of the full A–F lifecycle this issue describes. The remaining phases and write-capable interception should be designed against this issue's scope.