chore: install rector with accept-current-state baseline

Installs rector/rector ^2.0 (v2.4.2) + driftingly/rector-laravel
^2.0 as dev-dependencies. Configures PHP 8.2 language sets + safe
quality rule sets (CODE_QUALITY, DEAD_CODE, EARLY_RETURN,
TYPE_DECLARATION, PRIVATIZATION) + Laravel-specific sets
(LARAVEL_CODE_QUALITY, LARAVEL_COLLECTION).

Dry-run baseline: 487 rule-applications across 357 files. NO
changes applied in this commit — adoption is incremental via per-
set sprints documented in BACKLOG.md.

Top rules by volume:
  103  AddClosureVoidReturnTypeWhereNoReturnRector
   71  AddArrowFunctionReturnTypeRector
   51  AppToResolveRector
   34  ConvertStaticToSelfRector
   27  ReadOnlyClassRector
   18  NullToStrictStringFuncCallArgRector
   16  ReturnBinaryOrToEarlyReturnRector
   16  MakeModelAttributesAndScopesProtectedRector
   13  RemoveUnusedVariableAssignRector
   13  OptionalToNullsafeOperatorRector
   13  FlipTypeControlToUseExclusiveTypeRector

Composer scripts:
  - composer rector              — DRY-RUN (default)
  - composer rector:apply        — apply changes
  - composer rector:clear-cache  — clear Rector cache

Dry-run exits with code 2 when suggestions exist (Rector convention,
not an error state). Apply-mode exits 0 on clean runs.

Documentation: /dev-docs/RECTOR.md added; CLAUDE.md updated.

Backlog: per-set application sprints seeded
(TECH-RECTOR-01..05 + TECH-RECTOR-CI). DEAD_CODE (smallest scope)
and TYPE_DECLARATION (biggest volume, will help reduce Larastan
baseline) are the natural first two.

Disruptive sets deliberately deferred:
  - LaravelLevelSetList::UP_TO_LARAVEL_* — broad bulk upgrades
  - SetList::NAMING — high-churn variable renames
  - SetList::INSTANCEOF — substantial logic changes

Memory limit 2G (dry-run completed within it).

No production behavior change. No code modified — Rector ran
dry-run only.

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

CLAUDE.md

@@ -19,6 +19,9 @@ Design document: `/dev-docs/design-document.md`
 - `composer analyse` — Larastan static analysis at level 6 with
   accept-all baseline. New errors beyond the baseline must be fixed
   before merge. See `/dev-docs/LARASTAN.md`.
+- `composer rector` — Rector dry-run for modernisation suggestions.
+  See `/dev-docs/RECTOR.md`. Apply only in scoped sprints, never
+  automatically.
 
 ## Repository layout