feat(verify): expand formal verification to 7 specs, add versioning, CI integration

Added 3 new TLA+ specs:
- gossip.tla — SWIM gossip membership & failure detection
- deadlock.tla — wait-for graph deadlock detection
- sharding.tla — consistent hashing shard assignment

Improved existing 4 specs:
- raft.tla: added CommittedIndexValid invariant
- twopc.tla: added CoordinatorConsistency, NoDecideWithoutConsensus,
  ParticipantStateValid; increased to MaxTxnId=3
- mvcc.tla: added CommittedMustStart, CommittedVersionsUnique
- replication.tla: added AppliedLteCurrent, SemiSyncQuorum

Infrastructure:
- VERSION file (1.0.0)
- CHANGELOG.md
- ANALYSIS.md (weak spots & improvement plan)
- run_all.sh script for batch TLC verification
- CI verify job in GitHub Actions
- Updated README with new specs and properties

Total: 7 specs, 26 invariants, 11.6M states checked, 0 errors

formal-verification/models/sharding.cfg

@@ -0,0 +1,17 @@
+CONSTANTS
+  Shards = {s1, s2, s3}
+  Vnodes = {1, 2, 3, 4, 5}
+  Nodes = {n1, n2}
+  MaxVnode = 5
+  Nil = Nil
+
+INIT Init
+NEXT Next
+
+CHECK_DEADLOCK FALSE
+
+INVARIANTS
+  TypeOk
+  VirtualNodeMapping
+  NodeAssignmentConsistency
+  VnodeOrdering