Add Rust standalone runtime baseline

[nicosuave]

Adds the Rust standalone runtime baseline across CLI, HTTP, MCP, LSP, workbench, Python bridge, DuckDB extension wiring, WASM, C ABI, and CI gates.

Also includes the inventory and follow-up documentation so the current state is explicit rather than implied: supported vs experimental surfaces, DuckDB ADBC proof, env-gated ADBC breadth, Python bridge strict-mode behavior, MCP/HTTP schema gaps, LSP/workbench limits, DuckDB extension/C ABI hardening, and packaging/CI follow-up work.

Important scope notes:

• This is not full Python parity.
• The Python Rust bridge is opt-in, not a transparent default replacement.
• DuckDB ADBC is proven locally; other ADBC drivers are documented as env-gated or future CI work.
• HTTP, MCP, LSP, and workbench are executable and tested but still experimental.
• Release automation is intentionally out of scope for this PR.

Validated locally with the strict Rust probe, Rust cargo test/clippy gates, Rust HTTP/MCP/LSP/workbench/ADBC targeted tests, Python ruff gates, and the full Python pytest suite.