feat(directives): unified contracts surface — backbone (#128)

This is the backbone PR for the unified directive workflow. A directive
holds a sequence of contracts; each contract is a spec body whose
execution drives tasks in the directive's shared worktree. Lifecycle
(Lock & Start, queue scheduler, drag-reorder) lands in follow-ups.

What's in this PR:
- Migration adds `position` (queue order) and `merge_mode`
  (shared|own_pr) columns to directive_documents. The actual table
  rename is deferred — the legacy `contracts` table from the old
  contracts system still exists, and the rename collision waits for
  Phase 5 to drop legacy contracts.
- Repository: list orders by position; create assigns next-position;
  update accepts merge_mode; new reorder_directive_document_position
  shifts siblings inside a transaction.
- HTTP: endpoints aliased under /api/v1/directives/{id}/contracts and
  /api/v1/contracts/{id}/... with a new /contracts/{id}/reorder.
- Frontend: api types renamed `DirectiveContract*` (avoiding the
  legacy `Contract` type collision); document-directives.tsx imports
  via aliases so the rest of the file is untouched.

Internal struct + table names stay `DirectiveDocument` /
`directive_documents` until the legacy contracts cleanup.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/makima/src/db/models.rs b/makima/src/db/models.rs
index 18f3435..fcccd05 100644
--- a/makima/src/db/models.rs
+++ b/makima/src/db/models.rs
@@ -2938,10 +2938,16 @@ pub struct UpdateDirectiveStepRequest {
 // Directive Document Types
 // =============================================================================
 
-/// A directive document — one of N markdown documents owned by a directive.
-/// The user calls these "directive contracts". Each document has its own
-/// lifecycle (draft → active → shipped → archived) and may be attached to a
-/// PR. Multiple documents can be active under the same directive at once.
+/// A directive document — the user-facing "contract" in the unified
+/// directive UI. One of N specs owned by a directive. Each runs
+/// sequentially in the directive's shared worktree (or, when
+/// `merge_mode = 'own_pr'`, on its own branch). `position` defines
+/// queue order.
+///
+/// Naming note: this struct stays `DirectiveDocument` internally because
+/// a legacy `Contract` struct (from the pre-directive contracts system)
+/// still exists. The API and frontend expose this as "Contract"; the
+/// table/struct rename lands once legacy contracts are dropped (Phase 5).
 #[derive(Debug, Clone, FromRow, Serialize, Deserialize, ToSchema)]
 #[serde(rename_all = "camelCase")]
 pub struct DirectiveDocument {
@@ -2956,6 +2962,12 @@ pub struct DirectiveDocument {
     pub shipped_at: Option<DateTime<Utc>>,
     pub archived_at: Option<DateTime<Utc>>,
     pub version: i32,
+    /// Queue position within the parent directive (0-indexed). Lower
+    /// numbers run earlier; only one contract is active at a time.
+    pub position: i32,
+    /// Where this contract's commits land. `shared` (default): the
+    /// directive's branch. `own_pr`: a contract-specific branch + PR.
+    pub merge_mode: String,
     pub created_at: DateTime<Utc>,
     pub updated_at: DateTime<Utc>,
 }