Normalize escaped multiline issue and approval text (#4444)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - The board and agent APIs accept multiline issue, approval,
interaction, and document text
> - Some callers accidentally send literal escaped newline sequences
like `\n` instead of JSON-decoded line breaks
> - That makes comments, descriptions, documents, and approval notes
render as flattened text instead of readable markdown
> - This pull request centralizes multiline text normalization in shared
validators
> - The benefit is newline-preserving API behavior across issue and
approval workflows without route-specific fixes

## What Changed

- Added a shared `multilineTextSchema` helper that normalizes escaped
`\n`, `\r\n`, and `\r` sequences to real line breaks.
- Applied the helper to issue descriptions, issue update comments, issue
comment bodies, suggested task descriptions, interaction summaries,
issue documents, approval comments, and approval decision notes.
- Added shared validator regressions for issue and approval multiline
inputs.

## Verification

- `pnpm exec vitest run --project @paperclipai/shared
packages/shared/src/validators/approval.test.ts
packages/shared/src/validators/issue.test.ts`
- `pnpm --filter @paperclipai/shared typecheck`

## Risks

- Low risk. This only changes text fields that are explicitly multiline
user/operator content.
- If a caller intentionally wanted literal backslash-n text in these
fields, it will now render as a real line break.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex, GPT-5 coding agent, tool-enabled with
shell/GitHub/Paperclip API access. Context window was not reported by
the runtime.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

packages/shared/src/validators/issue.ts

@@ -10,6 +10,7 @@ import {
   ISSUE_THREAD_INTERACTION_KINDS,
   ISSUE_THREAD_INTERACTION_STATUSES,
 } from "../constants.js";
+import { multilineTextSchema } from "./text.js";
 
 export const ISSUE_EXECUTION_WORKSPACE_PREFERENCES = [
   "inherit",
@@ -130,7 +131,7 @@ export const createIssueSchema = z.object({
   blockedByIssueIds: z.array(z.string().uuid()).optional(),
   inheritExecutionWorkspaceFromIssueId: z.string().uuid().optional().nullable(),
   title: z.string().min(1),
-  description: z.string().optional().nullable(),
+  description: multilineTextSchema.optional().nullable(),
   status: z.enum(ISSUE_STATUSES).optional().default("backlog"),
   priority: z.enum(ISSUE_PRIORITIES).optional().default("medium"),
   assigneeAgentId: z.string().uuid().optional().nullable(),
@@ -168,7 +169,7 @@ export type CreateIssueLabel = z.infer<typeof createIssueLabelSchema>;
 
 export const updateIssueSchema = createIssueSchema.partial().extend({
   assigneeAgentId: z.string().trim().min(1).optional().nullable(),
-  comment: z.string().min(1).optional(),
+  comment: multilineTextSchema.pipe(z.string().min(1)).optional(),
   reviewRequest: issueReviewRequestSchema.optional().nullable(),
   reopen: z.boolean().optional(),
   resume: z.boolean().optional(),
@@ -187,7 +188,7 @@ export const checkoutIssueSchema = z.object({
 export type CheckoutIssue = z.infer<typeof checkoutIssueSchema>;
 
 export const addIssueCommentSchema = z.object({
-  body: z.string().min(1),
+  body: multilineTextSchema.pipe(z.string().min(1)),
   reopen: z.boolean().optional(),
   resume: z.boolean().optional(),
   interrupt: z.boolean().optional(),
@@ -213,7 +214,7 @@ export const suggestedTaskDraftSchema = z.object({
   parentClientKey: z.string().trim().min(1).max(120).nullable().optional(),
   parentId: z.string().uuid().nullable().optional(),
   title: z.string().trim().min(1).max(240),
-  description: z.string().trim().max(20000).nullable().optional(),
+  description: multilineTextSchema.pipe(z.string().trim().max(20000)).nullable().optional(),
   priority: z.enum(ISSUE_PRIORITIES).nullable().optional(),
   assigneeAgentId: z.string().uuid().nullable().optional(),
   assigneeUserId: z.string().trim().min(1).nullable().optional(),
@@ -439,7 +440,7 @@ export type RejectIssueThreadInteraction = z.infer<typeof rejectIssueThreadInter
 
 export const respondIssueThreadInteractionSchema = z.object({
   answers: z.array(askUserQuestionsAnswerSchema).max(20),
-  summaryMarkdown: z.string().max(20000).nullable().optional(),
+  summaryMarkdown: multilineTextSchema.pipe(z.string().max(20000)).nullable().optional(),
 });
 export type RespondIssueThreadInteraction = z.infer<typeof respondIssueThreadInteractionSchema>;
 
@@ -462,7 +463,7 @@ export const issueDocumentFormatSchema = z.enum(ISSUE_DOCUMENT_FORMATS);
 export const upsertIssueDocumentSchema = z.object({
   title: z.string().trim().max(200).nullable().optional(),
   format: issueDocumentFormatSchema,
-  body: z.string().max(524288),
+  body: multilineTextSchema.pipe(z.string().max(524288)),
   changeSummary: z.string().trim().max(500).nullable().optional(),
   baseRevisionId: z.string().uuid().nullable().optional(),
 });