drop legacy summaryCommentNodeId column (#617)

Was retained on `workflow_runs` after PR #568 replaced the comment-based
summary path with the snapshot architecture, with a "kept for backfill of
pre-snapshot runs" annotation. No backfill is planned: pre-snapshot summary
comments were written in the user-facing PR_SUMMARY_FORMAT (TL;DR + key
changes blockquote + before/after sections), not the agent-context
functional-summary format the snapshot now expects. Backfilling them would
prime new runs with the wrong shape and pollute the agent context. Old
comments stay on github.com as historical artifacts; the column on the DB
row is dead weight.

Strips the field from:
- prisma schema + new migration `20260508190000_drop_summary_comment_node_id`
- `app/api/workflow-run/[runId]/route.ts` STRING_FIELDS allowlist
- `action/utils/patchWorkflowRunFields.ts` type union + STRING_KEYS
- `utils/db/selectActiveWorkflowRuns.ts` select clause
- `utils/github/enrichWorkflowRunsWithArtifactUrls.ts` node-id type, URL
  resolution, collectUniqueNodeIds + urlsForRun
- `utils/webhooks/handleWorkflowRunWebhook.ts` two select clauses, the
  hasRecordedArtifact param, and the orphaned-leaping-comment alert text
- `components/RunArtifactPills.tsx` ArtifactKey union + ARTIFACT_KEYS +
  switch cases (drops the "View summary" chip from the workflow run list)

Verified: pnpm typecheck clean, pnpm lint clean (537 files), action build
clean. Dev DB reset against production parent and the migration applied
cleanly — column is gone from the workflow_runs table.

utils/patchWorkflowRunFields.ts

@@ -14,7 +14,6 @@ export type WorkflowRunArtifactPatchKey =
   | "issueNodeId"
   | "reviewNodeId"
   | "planCommentNodeId"
-  | "summaryCommentNodeId"
   | "summarySnapshot";
 
 /**
@@ -38,7 +37,6 @@ const STRING_KEYS: WorkflowRunArtifactPatchKey[] = [
   "issueNodeId",
   "reviewNodeId",
   "planCommentNodeId",
-  "summaryCommentNodeId",
   "summarySnapshot",
 ];