Self-host M2: spine inventory coverage drift guard (595→603 file list)

[PurHur]

Problem

M2 spine smoke links 595 / 603 inventory files (#1872 SSOT: php script/bootstrap-spine-count.php). check-selfhost-spine-count-sync.php only guards counts in docs — it does not fail when specific inventory paths are still absent from test/selfhost/compiler_lib_spine_smoke/main.php.

Contributors closing #1922 grep bootstrap-inventory.php by hand instead of a deterministic missing-file list.

Goal

Add script/check-selfhost-spine-coverage-sync.php (+ optional SELFHOST_SPINE_COVERAGE_SYNC_GATE=1 in ci-fast.sh inventory checks):

1. Parse inventory file list from php script/bootstrap-inventory.php --json (or parse docs/bootstrap-inventory.md table)
2. Parse require_once paths from compiler_lib_spine_smoke/main.php
3. Exit 1 with sorted list of missing lib/*.php paths (max 20 printed, full list to /tmp or --verbose)
4. Exit 0 when spine includes all 603 inventory files

Implementation hints

Piece	Path	Notes
Checker	script/check-selfhost-spine-coverage-sync.php	Mirror style of check-selfhost-spine-count-sync.php
Helper	Reuse bootstrap_count_spine_requires() from script/bootstrap-spine-count.php	Avoid duplicating regex
Inventory	script/bootstrap-inventory.php	--check already knows 603 files
Dev helper	script/bootstrap-selfhost-next-includes.php --bundle=...	Document in checker stderr footer
CI	script/ci-common.sh ci_run_inventory_checks()	Default on; opt-out SELFHOST_SPINE_COVERAGE_SYNC_GATE=0 during bulk spine PRs
Test	test/unit/SelfhostSpineCoverageSyncTest.php	Fixture: temp spine missing one file → exit 1

Suggested output

check-selfhost-spine-coverage-sync: FAILED — 8 inventory files missing from spine:
  lib/JIT/Builtin/Type/Foo.php
  ...
Next: php script/bootstrap-selfhost-next-includes.php --bundle=test/selfhost/compiler_lib_spine_smoke/main.php --limit=8

Acceptance criteria

• Checker lists exactly the gap between inventory and spine on master today (8 files until Self-host M2: Close compiler_lib_spine_smoke gap (589→593 inventory units) #1922 lands)
• ./script/ci-fast.sh runs checker when gate=1
• test/unit/SelfhostSpineCoverageSyncTest.php green
• ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 + Self-host M2: Close compiler_lib_spine_smoke gap (589→593 inventory units) #1922 link this issue

Verification (local / Docker only)

php script/check-selfhost-spine-coverage-sync.php
php script/bootstrap-inventory.php --check
./script/ci-fast.sh --filter SelfhostSpineCoverage
docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev \
  php script/check-selfhost-spine-coverage-sync.php

No GitHub Actions (#394 ✅).

Dependencies

• Self-host M2: Close compiler_lib_spine_smoke gap (589→593 inventory units) #1922 — consumer: land missing require_once until checker green
• Self-host: Single source of truth for M2 spine unit counts (584/585/586/588 drift) #1872 ✅ — count SSOT (keep both gates; coverage is stricter)

Links

• Epic Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 · ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 Phase 5 Self-host
• Hygiene (orthogonal): check-m2-spine-issue-hygiene.php (DevEx: Close stale m2-spine-unit issues when file already in compiler_lib_spine_smoke #1808)

[PurHur]

claim: cursor-agent-lane-b — bootstrap fallback: close 13-file spine coverage drift (check-selfhost-spine-coverage-sync 3083→3096/3096). Lane-B queue empty (#11437/#11428 closed).

[PurHur]

Merged via PR #11502 — spine coverage drift closed.

Fix

Added 13 missing require_once units to compiler_lib_spine_smoke/main.php; synced footnotes + BootstrapSelfhostBundleTest to 3096/3096.

Verification

php script/check-selfhost-spine-coverage-sync.php  # OK 3096/3096
make north-star5-verify-fast                        # OK
php bin/compile.php -l test/selfhost/compiler_lib_spine_smoke/main.php  # OK (Docker)

claim released: cursor-agent-lane-b