docs(readme): rewrite root README to be MCP-prominent and listing-rich

[Declade]

Why

The old root README was a 1099-byte monorepo stub that just listed 4 packages and pointed at per-language READMEs. This makes:

• the mcp.so Overview tab effectively empty (mcp.so scrapes the root README)
• the Glama Overview block thin
• the pending awesome-mcp-servers PR #5905 hard for reviewers to assess
• direct GitHub visitors land on a stub that doesn't actually sell what Lucairn does

What

Single-file diff: README.md only.

The rewrite leads with the highest-leverage discovery path (the MCP one-liner + JSON config snippet), then explains the 3-layer sanitizer pipeline, then provider routing, then the existing per-language SDK table, then sign-up + verify flow.

Constraints respected

• Brand: Lucairn (one c); zero "The Veil" / dsaveil.io / veil_live_* / @dsaveil/... mentions.
• Tier names: Developer / Pro / Enterprise only — no Pro+ / pro_plus / Solo Free / Solo Pro.
• Sub-processor mentions stay inside the locked allowlist (no Ollama, no Qwen).
• Mechanism allowlist respected: no TLS version claims, no SOC 2, no ISO 27001, no HIPAA, no "red team", no uptime SLAs.
• Custom-trained PII shield is framed Enterprise-only.
• "no raw identity data leaves your environment" is scoped to Enterprise self-host only; Developer hosted is "on-gateway pseudonymization before your LLM sees the request."

Drift caught + fixed

• The mcp-server row in the package-identifier table said 1.0.0; the package is actually published at 1.1.0 (CLAUDE.md notes 1.0.1 was published 2026-05-04, and the source mcp-server/package.json is now at 1.1.0 per the Stage 4 cross-provider BYOK ship). Bumped the table accordingly.
• Cross-provider BYOK now explicitly attributed to @lucairn/mcp-server@1.1.0.

Banned-literal sweep

rg -n 'dsaveil\.io|veil_live_|@dsaveil/|"The Veil"|tracevault_app|Pro\+|pro_plus|Solo Free|Solo Pro|Ollama|Qwen|TLS 1\.[0-9]|E2E encryption|SOC ?2|ISO ?27001|HIPAA|PCI-DSS|red team' README.md

Returns zero matches.

Files touched

• README.md (123 line diff: +105 / -18; final ~120 lines)