perf(test): make schema-dump target + opt-in fast-path docs (WS-6)

Session 2.6's per-test migrate:fresh in 4 backfill test classes
replays ~120 migrations. Laravel's schema:dump produces a single
SQL file that migrate:fresh loads atomically when present —
significantly faster on environments where the host has the
\`mysql\` CLI available for Laravel's load step.

Changes:
- New Makefile target \`schema-dump\` runs mysqldump INSIDE the
  bm_mysql Docker container (no host mysqldump dependency to
  GENERATE the dump). Outputs api/database/schema/mysql-schema.sql.
- api/database/schema/.gitignore added: mysql-schema.sql is NOT
  committed by default. Laravel's auto-load on migrate:fresh
  shells out to the host's \`mysql\` CLI; on hosts without it,
  the presence of the dump file actively breaks migrate (exit 127).
  Treat the dump as opt-in per dev environment.
- CLAUDE.md "Schema dumps (opt-in fast path)" subsection added with
  the workflow: brew install mysql-client → migrate to head →
  make schema-dump → optionally commit.

phpstan-baseline.neon: removed a stale "unused use \$actor" entry
in FormSubmissionService whose underlying closure pint cleaned up
in commit 060d6f3 (Task 1).

Wall-time on this dev machine (no host mysql CLI): NO speedup,
backfill tests still ~6s per setUp. The dump file is ready for
environments that have mysql CLI. Documented as a deviation.

JSON canonicalization (commit 060d6f3) is the load-bearing
correctness fix from this branch; the schema-dump perf path is a
nice-to-have that activates per-environment.

Refs: WS-6 session 2.6 deviation #5 cleanup

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help services services-stop api app portal docs migrate fresh db-shell test test-db-create
+.PHONY: help services services-stop api app portal docs migrate fresh db-shell test test-db-create schema-dump
 
 # Colors
 GREEN  := \033[0;32m
@@ -27,6 +27,7 @@ help:
 	@echo "    make fresh            Fresh migrate + seed"
 	@echo "    make db-shell         Open MySQL shell"
 	@echo "    make test-db-create   Create crewli_test database (one-time)"
+	@echo "    make schema-dump      Regenerate MySQL schema dump (run after new migrations)"
 	@echo ""
 	@echo "  $(YELLOW)Testing:$(NC)"
 	@echo "    make test             Run PHPUnit suite (creates crewli_test if needed)"
@@ -81,3 +82,23 @@ test-db-create:
 
 test: test-db-create
 	@cd api && php artisan test
+
+# Regenerate api/database/schema/mysql-schema.sql from the current
+# crewli_test schema. Runs mysqldump INSIDE the bm_mysql Docker
+# container, so contributors don't need mysqldump on the host.
+#
+# Workflow: this target dumps WHATEVER state crewli_test is currently
+# in. Run `make test-db-create` (creates DB), then put it at the desired
+# state — typically by running the test suite, which migrates the test
+# DB to head — then `make schema-dump`.
+#
+# See CLAUDE.md "Schema dumps" — commit the regenerated dump alongside
+# any new migrations so CI / fast-path migrate:fresh stays in sync.
+schema-dump:
+	@echo "$(GREEN)Regenerating api/database/schema/mysql-schema.sql from current crewli_test state...$(NC)"
+	@docker exec bm_mysql mysqldump --no-tablespaces --skip-add-locks --skip-comments --skip-set-charset --tz-utc -u root -proot crewli_test --routines --no-data 2>/dev/null > /tmp/crewli-schema-structure.sql
+	@docker exec bm_mysql mysqldump --no-tablespaces --skip-add-locks --skip-comments --skip-set-charset --tz-utc -u root -proot crewli_test migrations --no-create-info 2>/dev/null > /tmp/crewli-schema-migrations.sql
+	@cat /tmp/crewli-schema-structure.sql /tmp/crewli-schema-migrations.sql > api/database/schema/mysql-schema.sql
+	@rm /tmp/crewli-schema-structure.sql /tmp/crewli-schema-migrations.sql
+	@echo "$(GREEN)✓ api/database/schema/mysql-schema.sql updated$(NC)"
+	@echo "$(YELLOW)Note: Commit the updated schema dump alongside any new migrations.$(NC)"