Self-host: namespace support blocks compiling lib/ (bootstrap gate)

[PurHur]

Problem

bin/vm.php path inventory includes 297 eligible files, all under namespace PHPCompiler. AOT/JIT compile of any lib/*.php entry requires lowering namespaces (#84).

Bootstrap impact

Blocks self-hosting lib/Compiler.php, lib/Runtime.php, lib/VM.php until qualified names and use work in the static compiler.

Acceptance

• bin/compile.php -l succeeds on a single-namespaced fixture under test/bootstrap-aot/
• Inventory notes namespace as resolved for bootstrap subset

Tracks #212 / #78.