Rewrite README to match the current architecture

[johnnyclem]

What Changed

• Rewrote README.md from scratch to match the current codebase instead of a stale earlier API surface.
• Replaced the outdated tool-by-tool reference (save_concept_as_thoughtForm, convert_concept_from_*, etc.) with the tools actually registered in src/server.ts: save_concept, read_concept, delete_concept, list_concepts, batch_save_concepts, search_concepts, convert_concept, embed_text, health_check, get_stats, agentvault_backup, and the optional vault_* tools.
• Fixed the vector dimension inconsistency (README mixed 384 and 768; the actual value is VECTOR_DIMENSION = 384, all-MiniLM-L6-v2).
• Corrected the clone URL (yourusername/politician → johnnyclem/polytician).
• Documented the real env-var-driven configuration (POLYTICIAN_* variables in src/config.ts), namespaces + optimistic concurrency (expectedVersion), the Postgres/pgvector backend, and AES-256-GCM encrypted PolyVault backups.
• Clarified that the Python sidecar is optional (FAISS rebuild + PolyVault bundle ops only) and never auto-spawned, replacing installation steps that implied it was required for embeddings/NER.
• Added CI/npm/license/Node badges, a corrected architecture diagram, and accurate Docker Compose / Kubernetes deployment sections.
• Removed the outdated step-by-step tutorials that referenced tools/fields no longer in the codebase.

Why

The previous README described an earlier API surface and was already flagged in its own text as "pending a rewrite" — several examples referenced tools, field names, and a 768-dim vector size that don't exist in the current implementation, which would actively mislead new users and integrators.

Validation

• Documentation-only change; no code paths modified.
• Local checks run (describe below) — not applicable, no source changes.

# N/A — README.md only

Risks / Rollback

• Risk level: low
• Rollback plan: revert this commit; no code or schema changes are included.

Notes for Reviewers

• PolyVault guardrails checklist is out of scope — this PR only touches README.md.

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