Split the body of load_config_in into a load_single_layer(cwd, path) helper that
loads and fully processes one config file (version-gating, legacy scan, normalize)
— the seam the upcoming layered loader needs — while load_config_in keeps its exact
single-layer semantics (an explicit --config still errors on a missing file).
Add the precedence-ordered Layer enum (Default < Global < State < Project) and a
Provenance side-table newtype for the merge engine, plus the dirs dependency
(already in the lock tree via lance, so zero new crates). No behavior change.
`#[serde(deny_unknown_fields)]` was applied unconditionally as a struct
attribute, so the `version` discriminator did not actually gate strictness: a
legacy (no-`version:`) config was wrongly rejected for any unrecognized key,
contradicting the documented contract (RFC-002 §3: no version = legacy-lenient,
`version: 1` = strict) and the code's own comments.
Make strictness a function of `version`, decided at one point in
`load_config_in`: parse once via `serde_ignored` (collecting ignored fields at
all depths), then reject unknowns only under `version: 1`; legacy tolerates them
(restoring the pre-existing behavior). Drop `deny_unknown_fields` from the two
legacy-spanning structs (`OmnigraphConfig`, `TargetConfig`) and keep it on the
v1-only typed blocks (`StorageBlock`, `ServerEntry`), which have no legacy form.
This removes the double-parse (`check_config_version` is gone — the version is
read from the parsed struct) and makes v1 strictness comprehensive: a misspelled
nested key (e.g. under `cli:`) now errors instead of being silently dropped.
Turns the previous commit's regression test green and pins v1 comprehensive
strictness.
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.
