v0.2.0 (1/N): public API surface — interfaces + BridgeOp enum

Establishes the contract layer the rest of v0.2.0 builds on. Pre-1.0
SemVer break: ModelPublisher::publishEntityChange() now takes BridgeOp
instead of a raw string.

Interfaces (Symfony idiom: same namespace as concrete, like HubInterface
next to Hub):
  - PublisherInterface — publish(string, array, bool)
  - ModelPublisherInterface — publishEntityChange(object, BridgeOp)
  - CorrelationContextInterface — set/get/clear

App code should typehint these instead of the concretes so swappable
implementations (offline-buffer publisher, multi-hub fan-out, request-
stamp correlation) remain non-breaking. Concrete classes implement them
unchanged; autowire continues to inject the implementations transparently.

BridgeOp: PHP 8.1 string-backed enum with cases Upsert / Delete /
Replace / Event matching PLAN.md §4's envelope `op` wire format.
Internal call sites updated; tests use the cases directly.

Switched typehints:
  - ModelPublisher ctor: PublisherInterface + CorrelationContextInterface
  - DoctrineBridgeListener ctor: ModelPublisherInterface
  - HealthController ctor: PublisherInterface (still emits `Publisher`
    as bundle canary value — `::class` resolves to the concrete class
    name regardless of typehint, so bundled-supervisor.sh's grep stays
    green)
  - skeleton PingController ctor: PublisherInterface (canonical app
    pattern — example/todo has no Publisher consumer to update)

Drive-by: removed deprecated setAccessible(true) call in
ModelPublisher::extractId — PHP 8.1+ allows reflection without it.

PHPStan + cs-fixer + PHPUnit (17/17) + maker snapshot all pass; dev
container compiles in the example app.

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

framework/php/src/CorrelationContext.php

@@ -5,17 +5,18 @@ declare(strict_types=1);
 namespace PhpQml\Bridge;
 
 /**
- * Per-request correlation key holder.
+ * Default implementation of {@see CorrelationContextInterface}: a plain
+ * per-request holder for the `Idempotency-Key` value.
  *
- * The HTTP request's `Idempotency-Key` (PLAN.md §4 *Idempotency*) is
- * stashed here on RequestEvent and read back by ModelPublisher when
- * it builds Mercure envelopes, so QML clients can match Mercure echoes
- * to the optimistic mutation that originated them (§5).
+ * Stashed here on RequestEvent (see {@see EventSubscriber\CorrelationKeyListener})
+ * and read back by {@see ModelPublisher} when it builds Mercure envelopes,
+ * so QML clients can match Mercure echoes to the optimistic mutation that
+ * originated them (PLAN.md §4 *Idempotency*, §5 *Optimistic updates*).
  *
  * Cleared on TerminateEvent. CLI commands and out-of-request mutations
  * see no correlation key, which is the correct behaviour.
  */
-final class CorrelationContext
+final class CorrelationContext implements CorrelationContextInterface
 {
     private ?string $key = null;