CI: Default WAVE3_ROADMAP_SYNC_GATE=1 in ci-fast after #1811 doc sync

[PurHur]

Problem

#1802 ✅ added script/check-wave3-roadmap-sync.php and Wave3RoadmapSyncTest, but the gate is opt-in (WAVE3_ROADMAP_SYNC_GATE=1). docs/roadmap-wave3.md drifted again (lists closed wave-3 issues as open).

Contributors can merge language/stdlib PRs without updating the wave-3 table until someone manually runs the checker.

Goal

After #1811 lands (doc matches 12/13 + 13/13):

1. Default WAVE3_ROADMAP_SYNC_GATE=1 in script/ci-defaults.env
2. Run ci_run_wave3_roadmap_sync() from script/ci-fast.sh (already wired in ci-common.sh)
3. Opt-out: WAVE3_ROADMAP_SYNC_GATE=0 for doc-only iteration
4. Document in docs/README.md and phpc doctor --gates if applicable

Implementation hints

File	Change
script/ci-defaults.env	WAVE3_ROADMAP_SYNC_GATE="${WAVE3_ROADMAP_SYNC_GATE:-1}"
script/ci-fast.sh	Ensure ci_run_wave3_roadmap_sync called (verify #1802 wiring)
test/unit/CiScriptsTest.php	Assert default-on in ci-fast
docs/roadmap-wave3.md	Must pass checker before flip PR merges

Acceptance criteria

./script/ci-fast.sh   # includes wave3 sync without manual export
docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev ./script/ci-fast.sh

Fails with clear message when docs/roadmap-wave3.md drifts from #1380 / spine counts.

Dependencies

• CI: Wave 3 roadmap drift guard (docs/roadmap-wave3.md vs #1380) #1802 ✅ checker
• Docs: Sync docs/roadmap-wave3.md to 12/13 language — only #1354 open #1811 — doc sync PR (blocker for default-on)
• Roadmap wave 3: full PHP language + stdlib gaps tracker (#1354–#1379) #1380 — umbrella counts

Non-goals

• GitHub Actions workflow (Disable github actions for now #394 ✅ closed)

Links

• ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 Phase 0
• Wave 3 close-out: land remaining language + debug_backtrace (#1380 finish line) #1751 wave 3 close-out

[PurHur]

Blocker cleared — ready for implementation (2026-05-25)

#1811 ✅ closed via #1815 — docs/roadmap-wave3.md now reflects 12/13 language + 13/13 stdlib.

This issue is unblocked. Suggested PR scope:

1. script/ci-defaults.env — WAVE3_ROADMAP_SYNC_GATE="${WAVE3_ROADMAP_SYNC_GATE:-1}"
2. test/unit/CiScriptsTest.php — assert default-on
3. phpc doctor --gates if applicable
4. Opt-out documented: WAVE3_ROADMAP_SYNC_GATE=0

Verify: ./script/ci-fast.sh (Docker: php-compiler:22.04-dev).