// Package service is spec.sr.ht's orchestration layer: the single seam that
// REST, MCP, GraphQL and the web UI all call, and the only place where git,
// Postgres and identity are allowed to meet.
//
// Dependency direction is strictly downward. This package imports core, gitx,
// db and authn; nothing above it may touch gitx or db directly. That rule is
// what keeps the three agent-facing surfaces behaviourally identical — they
// share these functions rather than each re-deriving the rules.
//
// # What Phase 1 contains
//
// Reads, validation and repair. Concretely:
//
//   - Wiring: [Config] and [New] assemble a [Service] from the shared
//     SourceHut config.ini, failing loudly at startup on a missing key rather
//     than deep inside the first request.
//   - Space lifecycle: [Service.CreateSpace], [Service.OpenSpace],
//     [Service.ListSpaces].
//   - Reads: [Service.ReadDocument], [Service.ListDocuments],
//     [Service.Policy] — each resolving either the approved head or a pinned
//     revision through the same code path, because there is one storage tier
//     and no checkout.
//   - Push validation: [Service.ValidatePush], the function the `update` hook
//     calls over RPC before a ref moves.
//   - Repair: [Reconcile] and [Service.RunReconciler].
//
// The write plane — propose, If-Match resolution, merge, auto-merge policy,
// digest bookkeeping — is Phase 3 and is deliberately absent.
//
// # One storage tier
//
// Every read resolves a git revision and reads blobs. The approved head, a
// pinned ?rev=<sha> and a proposal branch are the same call with a different
// revision string; an empty revision means "the approved head", which is what
// makes "reads default to the approved revision" a property of this layer
// rather than of each caller.
//
// # Errors
//
// Callers above this layer must not need gitx or db to interpret a failure, so
// every error that leaves this package satisfies one of the sentinels declared
// here ([ErrNotFound], [ErrSpaceExists], [ErrPushRejected], ...) as well as the
// lower-level class it came from. Multi-%w wrapping keeps both.
package service