feat(directives): per-PR revision snapshots + sidebar history (#112)

Stage 3 of the doc-mode revamp. Builds the foundation for treating contracts
as living specifications by freezing their content into a revision every
time a PR is raised.

## directive_revisions table (new migration)

(id, directive_id, content, pr_url, pr_branch, pr_state, version, frozen_at)
with UNIQUE(directive_id, version) and a partial index on pr_state='open'
so the next reconciler iteration can poll only what's still in flight.

pr_state is constrained to 'open' | 'merged' | 'closed' to mirror GitHub's
PR lifecycle. For Stage 3 we only freeze on PR creation; pr_state poll is
deferred to a follow-up.

## Repository helpers

- create_directive_revision: idempotent on (directive_id, pr_url) so a
  re-run of the orchestrator's completion task can't double-snapshot.
  Auto-assigns version = MAX(existing) + 1 per directive.
- list_directive_revisions_for_owner: scoped through the directive join
  so users can only read their own contract history.
- update_directive_revision_pr_state: stub for the upcoming poller.
- get_latest_merged_revision: returns the most recent merged revision —
  this is what Stage 4 will diff against on amendments.

## Snapshot trigger

update_directive handler now reads the BEFORE pr_url before the update.
If pr_url transitions None → Some, it snapshots the directive's current
goal as a revision tied to the new pr_url. Failures log and continue —
the directive update itself is unaffected.

## API + OpenAPI

GET /api/v1/directives/{id}/revisions returns DirectiveRevisionListResponse
(revisions newest-first). Schemas registered in OpenAPI.

## Frontend: revisions/ subfolder + read-only viewer

Each contract folder now has a third subfolder ("revisions/") that lazily
fetches and lists past revisions when the parent directive folder is open.
Empty contracts skip the subfolder entirely so brand-new ones aren't
cluttered. Each row shows v<N>.md plus a small pill ('open'/'merged'/
'closed').

Selecting a revision encodes itself into the existing ?task= param as
"revision:<id>", so EditorShell can route between the live task stream
(realTaskId), the read-only RevisionViewer (revisionId), or the editor
itself (neither). The viewer renders the frozen markdown verbatim with
a deep-link to the PR — these are immutable historical records, not edit
surfaces.

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

1 files changed, 98 insertions, 2 deletions

diff --git a/makima/src/server/handlers/directives.rs b/makima/src/server/handlers/directives.rs
index 44bf4ac..91f5892 100644
--- a/makima/src/server/handlers/directives.rs
+++ b/makima/src/server/handlers/directives.rs
@@ -11,12 +11,14 @@ use uuid::Uuid;
 use crate::db::models::{
     CleanupResponse, CreateDirectiveRequest, CreateTaskRequest,
     CreateDirectiveStepRequest, Directive, DirectiveListResponse,
-    DirectiveStep, DirectiveWithSteps, PickUpOrdersResponse,
+    DirectiveRevision, DirectiveStep, DirectiveWithSteps, PickUpOrdersResponse,
     UpdateDirectiveRequest, UpdateDirectiveStepRequest, UpdateGoalRequest,
     CreateDirectiveOrderGroupRequest, DirectiveOrderGroup,
     DirectiveOrderGroupListResponse, UpdateDirectiveOrderGroupRequest,
     OrderListResponse,
 };
+use serde::Serialize;
+use utoipa::ToSchema;
 use crate::db::repository;
 use crate::orchestration::directive::{
     build_cleanup_prompt, build_order_pickup_prompt, classify_goal_change,
@@ -185,8 +187,50 @@ pub async fn update_directive(
             .into_response();
     };
 
+    // Capture the BEFORE state so we can detect a pr_url transition (null
+    // → some-value), which is when the orchestrator's completion task has
+    // raised a PR for this directive. That transition is the trigger for
+    // freezing a directive_revisions snapshot.
+    let before_pr_url = match repository::get_directive_for_owner(pool, auth.owner_id, id).await {
+        Ok(Some(d)) => d.pr_url.clone(),
+        _ => None,
+    };
+
     match repository::update_directive_for_owner(pool, auth.owner_id, id, req).await {
-        Ok(Some(directive)) => Json(directive).into_response(),
+        Ok(Some(directive)) => {
+            // Detect "PR was just raised" — pr_url went from None to Some.
+            // Snapshot the current goal as a revision tied to this PR.
+            // Best-effort: a snapshot failure should not fail the update,
+            // because the directive's pr_url has already been written.
+            if before_pr_url.is_none() {
+                if let Some(ref new_pr_url) = directive.pr_url {
+                    if let Err(e) = repository::create_directive_revision(
+                        pool,
+                        directive.id,
+                        &directive.goal,
+                        new_pr_url,
+                        directive.pr_branch.as_deref(),
+                    )
+                    .await
+                    {
+                        tracing::warn!(
+                            directive_id = %directive.id,
+                            pr_url = %new_pr_url,
+                            error = %e,
+                            "Failed to snapshot directive revision on PR creation — \
+                             continuing; revision history will be incomplete"
+                        );
+                    } else {
+                        tracing::info!(
+                            directive_id = %directive.id,
+                            pr_url = %new_pr_url,
+                            "Snapshotted directive revision on PR creation"
+                        );
+                    }
+                }
+            }
+            Json(directive).into_response()
+        }
         Ok(None) => (
             StatusCode::NOT_FOUND,
             Json(ApiError::new("NOT_FOUND", "Directive not found")),
@@ -2038,3 +2082,55 @@ pub async fn pick_up_dog_orders(
     })
     .into_response()
 }
+
+// =============================================================================
+// Directive Revisions (per-PR snapshots)
+// =============================================================================
+
+#[derive(Debug, Serialize, ToSchema)]
+#[serde(rename_all = "camelCase")]
+pub struct DirectiveRevisionListResponse {
+    pub revisions: Vec<DirectiveRevision>,
+    pub total: i64,
+}
+
+/// List all per-PR revisions for a directive, newest first.
+#[utoipa::path(
+    get,
+    path = "/api/v1/directives/{id}/revisions",
+    params(("id" = Uuid, Path, description = "Directive ID")),
+    responses(
+        (status = 200, description = "Revision history", body = DirectiveRevisionListResponse),
+        (status = 503, description = "Database not configured", body = ApiError),
+    ),
+    security(("bearer_auth" = []), ("api_key" = [])),
+    tag = "Directives"
+)]
+pub async fn list_directive_revisions(
+    State(state): State<SharedState>,
+    Authenticated(auth): Authenticated,
+    Path(id): Path<Uuid>,
+) -> impl IntoResponse {
+    let Some(ref pool) = state.db_pool else {
+        return (
+            StatusCode::SERVICE_UNAVAILABLE,
+            Json(ApiError::new("DB_UNAVAILABLE", "Database not configured")),
+        )
+            .into_response();
+    };
+
+    match repository::list_directive_revisions_for_owner(pool, auth.owner_id, id).await {
+        Ok(revisions) => {
+            let total = revisions.len() as i64;
+            Json(DirectiveRevisionListResponse { revisions, total }).into_response()
+        }
+        Err(e) => {
+            tracing::error!("Failed to list directive revisions: {}", e);
+            (
+                StatusCode::INTERNAL_SERVER_ERROR,
+                Json(ApiError::new("LIST_FAILED", &e.to_string())),
+            )
+                .into_response()
+        }
+    }
+}