fix(serializer): key the registry by Type so name-colliding packets serialize - #505

The exceptions

Serializer keyed _packetSerializerDictionary by typeof(T).Name — the simple name. Ten packet class names exist in both a ClientPackets.* and a ServerPackets.* namespace; Initialize let the non-ClientPackets one win, so serializing the loser looked up the winner's compiled delegate and DynamicInvoke threw ArgumentException. (Deserializer never had the problem — it keys by wire header.)

The dictionary is private, so the fix keys it by Type: every packet keeps its own delegate, the ClientPackets-wins eviction logic is deleted, and the failure mode is gone rather than pinned. Serialize and the injected-sub-packet path look up by GetType() directly (also faster than string hashing).

Corpus/snapshot updates

• OnlyTheKnownSimpleNameCollisionsFailToSerialize → EveryPacketSerializes: zero tolerated exceptions.
• The snapshot now pins real wire output for all 398 packets; colliding simple names are disambiguated by namespace in the line ids so each line maps to exactly one type.
• CollidingPacketNamesAreStillDistinctTypes stays, now purely to catch new accidental duplicates.

Also fixes master's red CI

#498 was merged without being up to date with master, and #500/#501 had changed six packets (pstash/pstash_all headers, DmPacket/EventPacket/FbtPacket/RcPacket) after its snapshot was generated — so the snapshot test currently fails on master. The regenerated snapshot here is taken against current master and folds those in. Verified: every changed snapshot line traces to either the collision fix or those two merged PRs; all other 780+ lines are byte-identical.

127/127 tests pass locally.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Improved packet serialization reliability across client and server packet types.
  • Resolved serialization failures for several packets and handled similarly named packet types correctly.
  • Corrected serialized headers for stash-related packets.

• Tests

  • Expanded serializer coverage to include additional packet types.
  • Updated validation to require successful serialization for every packet and provide clearer type-specific failure details.