Move DEFAULT_DOCUMENT_AGENT_INSTRUCTIONS to constants

Mirrors the existing DEFAULT_MODERATOR_INSTRUCTIONS export so both
CorpusAction default-instruction strings live in one place per the
project's no-magic-strings convention. Importer site updated to pull
from constants instead of the local module-level binding.

Author: JSv4

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - `frontend/tests/CreateCorpusActionModal.ct.tsx` (+8 tests): analyzer-path validation, inline-agent validation (empty name / empty instructions), existing-agent-selection validation, successful inline-agent mutation, backend error toast, analyzer edit-mode pre-population, and legacy trigger-casing normalization fallback.
   - `frontend/tests/CorpusAgentManagement.ct.tsx` (+8 tests): query loading state, query error state, multi-tool badge overflow, inactive-status badge, update-mutation happy path, create-mutation backend-error toast, tool deselection, and edit-modal cancel.
   - `frontend/tests/CorpusDescriptionEditor.ct.tsx` (+7 tests): save failure (`ok: false`), save network-error path, reapply of snapshot-less version, twice-click collapse, Cancel Version Edit reset, fetch-md URL failure, and version-count pluralization.
+  - **Follow-up review polish**: moved `DEFAULT_DOCUMENT_AGENT_INSTRUCTIONS` from `CreateCorpusActionModal.tsx` into `frontend/src/assets/configurations/constants.ts` so both default-instruction strings (moderator + document agent) live in the single constants module per the project's no-magic-strings rule.
 - **Return-type annotations across core models and import/export pipeline** (Issue #1334, follow-up to #1331): The mypy gate wired in by #1331 recorded a 7208-error baseline frozen across 357 files. This PR pays down the annotation deficit on the core domain models and the bulk import/export tasks without touching runtime behavior or adding validators. Coverage jumped from the pre-issue numbers to:
   - `opencontractserver/corpuses/` 61.5% → 88.4% (target ≥80%)
   - `opencontractserver/annotations/` 48.1% → 93.8% (target ≥80%)

frontend/src/assets/configurations/constants.ts

@@ -538,3 +538,9 @@ export const DEFAULT_MODERATOR_INSTRUCTIONS = `You are a thread moderator for th
 3. Respond helpfully to user questions when appropriate
 
 You have access to thread context, messages, and moderation tools. Use them judiciously.`;
+
+// Default agent task instructions used when creating a document-processing
+// CorpusAction (rendered as the initial value when an add/edit document
+// trigger is selected).
+export const DEFAULT_DOCUMENT_AGENT_INSTRUCTIONS =
+  "You are a document processing agent for this corpus.";

frontend/src/components/corpuses/CreateCorpusActionModal.tsx

@@ -20,7 +20,10 @@ import { StyledTextArea } from "../widgets/modals/styled";
 import { toast } from "react-toastify";
 import _ from "lodash";
 import { OS_LEGAL_COLORS } from "../../assets/configurations/osLegalStyles";
-import { DEFAULT_MODERATOR_INSTRUCTIONS } from "../../assets/configurations/constants";
+import {
+  DEFAULT_DOCUMENT_AGENT_INSTRUCTIONS,
+  DEFAULT_MODERATOR_INSTRUCTIONS,
+} from "../../assets/configurations/constants";
 import { InlineBadge } from "../agents/AgentBadges";
 import { FormField } from "../widgets/form/FormField";
 
@@ -72,9 +75,6 @@ const DEFAULT_MODERATION_TOOLS = [
   { name: "unpin_thread", description: "Unpin a pinned thread" },
 ] as const;
 
-const DEFAULT_DOCUMENT_AGENT_INSTRUCTIONS =
-  "You are a document processing agent for this corpus.";
-
 /**
  * Shape of an existing corpus action for editing
  */