chore: bump version 0.5 → 0.6

v0.6.0 batches RAG quality batch:
- fb-38 score semantics (search_hit.v1 score_kind)
- fb-40 fact-grounded answer (rag-v2 prompt template)
- fb-42 bulk multi-query (kebab search --bulk + mcp__kebab__bulk_search)
- fb-39 eval foundation (precision_at_k_chunk metric)
- fb-39b embedding upgrade (multilingual-e5-large default)

embedding_version cascade triggers minor bump per design §9.

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

Cargo.toml

@@ -30,7 +30,7 @@ edition       = "2024"
 rust-version  = "1.85"
 license       = "MIT OR Apache-2.0"
 repository    = "https://github.com/altair823/kebab"
-version       = "0.5.0"
+version       = "0.6.0"
 
 [workspace.dependencies]
 anyhow       = "1"