Implement crash-safe streaming worker runtime

crates/remora-attempt/migrations/0005_checkpoint_staging_ownership.sql

@@ -0,0 +1,39 @@
+ALTER TABLE attempts
+    ADD COLUMN staging_origin_attempt_id TEXT;
+
+UPDATE attempts
+SET staging_origin_attempt_id = attempt_id;
+
+ALTER TABLE attempts
+    ALTER COLUMN staging_origin_attempt_id SET NOT NULL,
+    ADD CONSTRAINT attempts_staging_origin_fk
+        FOREIGN KEY (staging_origin_attempt_id)
+        REFERENCES attempts (attempt_id)
+        DEFERRABLE INITIALLY DEFERRED,
+    ADD CONSTRAINT attempts_id_job_unique UNIQUE (attempt_id, job_id);
+
+ALTER TABLE jobs
+    ADD COLUMN checkpoint_owner_attempt_id TEXT;
+
+UPDATE jobs j
+SET checkpoint_owner_attempt_id = (
+    SELECT a.attempt_id
+    FROM attempts a
+    WHERE a.job_id = j.job_id
+    ORDER BY a.fence DESC
+    LIMIT 1
+)
+WHERE j.checkpoint IS NOT NULL;
+
+ALTER TABLE jobs
+    ADD CONSTRAINT jobs_checkpoint_owner_fk
+        FOREIGN KEY (checkpoint_owner_attempt_id, job_id)
+        REFERENCES attempts (attempt_id, job_id)
+        DEFERRABLE INITIALLY DEFERRED,
+    ADD CONSTRAINT jobs_checkpoint_owner_check CHECK (
+        (checkpoint IS NULL) = (checkpoint_owner_attempt_id IS NULL)
+    );
+
+CREATE INDEX jobs_checkpoint_owner_idx
+    ON jobs (checkpoint_owner_attempt_id)
+    WHERE checkpoint_owner_attempt_id IS NOT NULL;

crates/remora-attempt/migrations/0006_staging_write_intents.sql

@@ -0,0 +1,9 @@
+ALTER TABLE attempt_staging_cleanup
+    DROP CONSTRAINT attempt_staging_cleanup_kind_check,
+    DROP CONSTRAINT attempt_staging_cleanup_identity_shape_check,
+    ADD CONSTRAINT attempt_staging_cleanup_kind_check
+        CHECK (kind IN ('write_intent', 'object', 'multipart')),
+    ADD CONSTRAINT attempt_staging_cleanup_identity_shape_check CHECK (
+        (kind IN ('write_intent', 'object') AND upload_id IS NULL)
+        OR (kind = 'multipart' AND version_id IS NULL AND upload_id IS NOT NULL)
+    );