v1.2 - Orphan Detector

Added — orphan detection (dead code)

• Orphaned symbols — top-level classes, interfaces, traits, enums, and global functions that
  nothing in the scanned set references. Same token engine, same zero-dependency, no-parser design as
  the clone side.
• Two run modes: orphans ride along in the default scan as an advisory (reported, but only
  clones set the exit code — safe for framework-heavy code where dynamic dispatch causes false
  positives); --orphans runs orphans-only and gates CI (a definite orphan → non-zero exit,
  exactly like a clone).
• Explains why something is dead, not just that it is:
  • Whole-file "unwired" — flags when every symbol declared in a file is itself an orphan (a
    stronger delete signal than one dead class among live ones). This is phpunused's "unreferenced
    file", done at symbol granularity.
  • "Superseded copy of ..." — reuses the clone engine: an orphan whose body duplicates a live
    symbol is annotated as the stale copy some refactor replaced but left behind. This is the
    orphan × clone synergy unique to phpcpd-next.
• Two confidence tiers (harvested from Psalm's UnusedClass / PossiblyUnusedClass split): a
  definite orphan is referenced nowhere and drives the exit code; a possible orphan is either
  a contract (interface / abstract class, which an out-of-tree package may implement) or a name that
  only appears in a string literal (a candidate for new $class / DI-container lookup) — reported for
  review, but does not fail the build.
• Entry-point awareness (harvested from shipmonk/dead-code-detector's usage providers): classes
  wired via framework attributes (#[Route], #[AsCommand], #[AsEventListener], #[Entity],
  #[Attribute], …) and *Test classes are recognised as reachable and never flagged.
• Suppression annotations: @api, @psalm-api, @phpstan-api, @phpcpd-keep, and
  @phpcpd-ignore-orphan in a symbol's docblock mark it intentionally public / kept.
• Better than a grep-based finder (the phpunused niche, done right): because detection is
  token-based, a name mentioned in a comment or the declaration itself no longer masks a real orphan,
  and a name in a string is scored as a weak dynamic signal rather than a hard reference. Reference
  detection is deliberately generous — over-counting hides a real orphan (safe), under-counting would
  tell someone to delete live code (never).
• Headless API LucianoPereira\PhpcpdNext\Orphans::detect(), mirroring Phpcpd::detect(), plus a
  new LucianoPereira\PhpcpdNext\Orphan\ subsystem (SymbolCollector, OrphanDetector, Symbol,
  Orphan, OrphanResult, OrphanTextReport). Covered by tests/OrphanDetectorTest.php (10 tests).
  Dogfooding the tool against src/ immediately surfaced a genuinely dead exception class
  (MissingResultException).