Self-host M2: native bin/vm.php -r smoke on compiler_lib_spine bundle

[PurHur]

Problem

M2 spine bundle compiler_lib_spine_smoke links natively (582/586 units, #1419, #1821) and prints a fixed probe string. M5 requires the real bin/vm.php driver path on the inventory — not a bespoke smoke binary.

Today there is no gate that:

1. Builds the spine AOT binary (make bootstrap-selfhost-lib-spine-smoke)
2. Runs bin/vm.php -r 'echo "vm-spine-ok\n";' semantics through the compiled bundle (or a thin wrapper that exercises VM dispatch from native code)

Contributors can grow the spine file count while the eventual bin/vm.php entry path remains untested.

Goal

Add bootstrap script + Makefile target:

BOOTSTRAP_LIB_SPINE_VM_SMOKE=1 make bootstrap-selfhost-lib-spine-vm-smoke
# stdout contains: vm-spine-ok

Uses the same spine link artifact as bootstrap-selfhost-lib-spine-smoke; adds a minimal -r echo (or test/bootstrap-aot/vm_spine_echo.php) executed via native VM entry.

Implementation hints

Piece	Location	Notes
Link	Makefile bootstrap-selfhost-lib-spine-smoke	Reuse build/selfhost-lib-spine binary
Entry	test/bootstrap-aot/vm_spine_echo.php or inline -r	Smallest VM path
Driver	bin/vm.php inventory subset	Defer full 586-file bundle to #1521 / #1492
CI	BOOTSTRAP_LIB_SPINE_VM_SMOKE_GATE=0 in ci-defaults.env	Opt-in in ci-local.sh llvm tail until green
Blockers	#1821 final Vm* units	May need spine growth first

Acceptance criteria

make bootstrap-wave-check
BOOTSTRAP_LIB_SPINE_VM_SMOKE=1 ./script/bootstrap-selfhost-lib-spine-vm-smoke.sh
# Docker:
docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev bash -lc \
  'BOOTSTRAP_LIB_SPINE_VM_SMOKE=1 make bootstrap-selfhost-lib-spine-vm-smoke'

Dependencies

• Epic Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 (M2→M5)
• M2 spine growth: batch tracker (compiler_lib_spine_smoke → full inventory) #1419 / Self-host M2: land final 3 ext/standard Vm* units in compiler_lib_spine_smoke (578→586) #1821 — spine growth
• M5: Bootstrap driver — run compiled bin/compile.php instead of Zend php #1521 — Zend-free bin/vm.php driver (M5; orthogonal)

Verification

Local/Docker only — no GHA (#394 ✅).

Links

• docs/bootstrap-selfhost.md, docs/self-host-target.md
• ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 Phase 5 Self-host

[PurHur]

Closed via #1850 — M2 lib spine VM -r smoke gate landed.