[AntPolkanov]

Description

✏️ "Rulekeeper" sounds like a place that stores rules, but the chat finds them. Someone suggested Rule Ferret, from "to ferret out", so I renamed it to The Ruleferret.

• I changed the name everywhere users see it: the search option, the search placeholder, the chat page title, error and refusal messages, and the system prompt.
• I renamed RulekeeperMark to RuleferretMark and askRulekeeper to askRuleferret. The chat event is now ruleferret:ask.
• I moved docs/rulekeeper/ to docs/ruleferret/ and renamed the two ADR files that had the old name. I updated the links between ADRs.
• I updated the name in comments, AGENTS.md, infra/README.md, .env.example and the index workflow name.
• I left the internal name "Rules Chat" alone. Azure resources, settings and .NET projects use that name, so nothing in the infrastructure changes.

Screenshot (optional)

✏️ Not added. Only label text changed, and the chat needs a signed-in account.

Validation

• pnpm lint: clean.
• pnpm test: 325 passed, 8 skipped. The search dialog tests check the new label.
• No file in the repo mentions "Rulekeeper" anymore.
• ap/rulekeeper-one-index-workflow also changes the index workflow and infra docs, so whichever merges second may need a small conflict fix.