Add the typed graph schema behind the version gate: per-graph storage: (string or block) XOR server:+graph_id:, a servers: map, and resolve_graph -> typed GraphLocator (local alias -> srv/gid qualified -> cli.graph default). uri stays a defaulted String filled by normalize_graphs from storage/server, so all existing .uri readers are unchanged and this commit is config-only (server reject-Remote is L5). deny_unknown_fields rejects typos; Storage has a hand-rolled string-or-block Deserialize for precise unknown-field errors. region/endpoint parsed but not yet engine-threaded (V2); GraphLocator.graph_id carried but unused on the wire until V2. 26 config tests pass; cargo test --workspace --locked green (per review).
load_config reads the optional top-level 'version:' discriminator and rejects unsupported versions (>1) before parsing; no-version (legacy) and 'version: 1' both still parse via the existing lenient struct. Forward-compat gate (RFC-002 §3) added as a no-op so the typed GraphLocator schema can tighten in following commits without breaking legacy files. 14 config tests pass (incl. version:1 parses, version:2 rejected).
Move config.rs (schema + loader + resolvers) into a new clean-leaf crate
(serde/serde_yaml/clap/color-eyre). The server aliases it via
`pub use omnigraph_config as config;` so every internal `config::` path and
the `pub use config::{...}` re-exports resolve unchanged. No behavior change;
the 12 config tests move verbatim and pass. First step of RFC-002 V0.
