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>

CLAUDE.md

@@ -100,7 +100,7 @@ When writing migrations or queries:
 - Use Laravel's query builder where possible — it handles cross-DB syntax consistently
 - For raw SQL, write MySQL syntax (no need for SQLite fallbacks). Index introspection: query `information_schema.STATISTICS`, never `sqlite_master`.
 - Foreign keys go on every relation column. The `nullOnDelete` / `cascadeOnDelete` choice is per the relationship's domain semantics; "no FK" is not an option.
-- Tests that round-trip JSON data via MySQL JSON columns must use `assertEquals` (structural equality) rather than `assertSame` on associative arrays — MySQL JSON may reorder object keys.
+- JSON values stored in byte-stable columns (`schema_snapshot`, webhook `payload_snapshot`, activity-log `properties` for diff payloads) MUST be canonicalized at write via `App\Support\Json\JsonCanonicalizer`. MySQL JSON columns may reorder associative-array keys on round-trip; canonicalize so re-emits / HMAC signatures / audit-replay diffs are byte-identical. Opaque-config JSON (`form_schemas.settings`, `translations`) is exempt — key order has no semantic meaning there. Tests on canonicalized data use `assertSame(JsonCanonicalizer::encode($a), JsonCanonicalizer::encode($b))`.
 
 Other database rules:
 
@@ -108,6 +108,37 @@ Other database rules:
 - Create migrations in dependency order: foundation first, then dependent tables
 - Always add composite indexes as documented in the design document (section 3.5)
 
+### Schema dumps (opt-in fast path)
+
+Laravel supports `database/schema/{driver}-schema.sql` as a fast-path
+baseline that `migrate:fresh` loads in one statement instead of replaying
+every migration. For Crewli's backfill / migration tests (which call
+`migrate:fresh` per test), this can yield a meaningful speedup —
+**when the host has the `mysql` and `mysqldump` CLI tools available.**
+
+Workflow:
+
+1. Install MySQL client tools on host (one-time):
+   ```bash
+   brew install mysql-client
+   echo 'export PATH="/opt/homebrew/opt/mysql-client/bin:$PATH"' >> ~/.zshrc
+   ```
+2. Bring `crewli_test` to head: `DB_DATABASE=crewli_test php artisan migrate --force`
+3. Generate the dump: `make schema-dump`
+4. Commit `api/database/schema/mysql-schema.sql` alongside any new migrations.
+
+The schema dump is **NOT committed by default** because Laravel's
+auto-load path shells out to the `mysql` CLI; on hosts without it,
+the presence of the dump file actively breaks `migrate` / `migrate:fresh`
+(load fails, exit 127). Treat the dump as opt-in per dev environment.
+
+`make schema-dump` runs `mysqldump` inside the `bm_mysql` Docker
+container, so contributors don't need `mysqldump` on the host to
+**generate** the dump — only to **load** it via Laravel's auto-detection.
+
+`--prune` is NOT used: individual migration files stay readable in
+`api/database/migrations/` for audit / rollback purposes.
+
 ### Roles and permissions
 
 - Use Spatie `laravel-permission`