feat(admin,core): image sub-fields in repeaters with media picker

[swissky]

What does this PR do?

Repeater rows previously rendered every non-scalar sub-field as a plain text input, so common shapes like photo galleries had to be built from hand-pasted URLs (full context in #1424). This adds first-class image sub-fields:

• Renderer — RepeaterField's sub-field switch gains case "image" and renders the same media-picker UI as top-level image fields (select / preview / change / remove), storing the same MediaValue shape; legacy string URLs still display via the existing backwards-compat path. New items initialize image sub-fields as null (instead of "").
• Reuse without a cycle — ImageFieldRenderer (+ its ImageFieldValue shape) moved verbatim from ContentEditor.tsx into its own module; ContentEditor imports RepeaterField, so importing back from ContentEditor would have been circular. No behavior change to top-level image fields.
• Schema builder — the sub-field type select offers Image (Lingui-wrapped like its siblings).
• Core whitelists — REPEATER_SUB_FIELD_TYPES / RepeaterSubField.type and the API Zod enum gain image. The Zod enum also gains the previously missing url entry — the builder UI and REPEATER_SUB_FIELD_TYPES already offered/documented it, but createFieldBody rejected it.

No new value-validation path is needed: repeater item values go through the existing z.unknown() repeater handling in the zod generator, identical to before.

Closes #1424

Process note: Ideas Discussion opened at #1428 (background analysis in issue #1424). Scope-guard note: 542 lines are dominated by the verbatim move of ImageFieldRenderer out of ContentEditor.tsx (no behavior change) plus tests — the net new logic is ~60 lines.

Type of change

• Bug fix
• Feature (requires maintainer-approved Discussion)
• Refactor (no behavior change)
• Translation
• Documentation
• Performance improvement
• Tests
• Chore (dependencies, CI, tooling)

Checklist

• I have read CONTRIBUTING.md
• pnpm typecheck passes (packages/admin + packages/core)
• pnpm lint passes (lint:quick clean)
• pnpm test passes (targeted: admin tests/components/RepeaterField.test.tsx 5/5 incl. 2 pre-existing datetime tests, FieldEditor.test.tsx 36/36, core field-validation-schema.test.ts 10/10; new tests red without the change)
• pnpm format has been run
• I have added/updated tests for my changes (if applicable)
• User-visible strings in the admin UI are wrapped for translation (the new Image select label uses the Lingui t macro; no messages.po changes included per CONTRIBUTING)
• I have added a changeset (@emdash-cms/admin minor, emdash minor)
• New features link to an approved Discussion: Image sub-fields in repeater fields (media picker in repeater rows) #1428 (pending maintainer approval; background in issue Repeater fields: no image/media subfield support (builder and renderer) #1424)

AI-generated code disclosure

• This PR includes AI-generated code — model/tool: Cursor + Fable 5 (reviewed and verified by a human before submission)

Screenshots / test output

❯ vitest run tests/components/RepeaterField.test.tsx   # without renderer change
  3 failed (image sub-field cases) | 2 passed (datetime)

❯ vitest run tests/components/RepeaterField.test.tsx tests/components/FieldEditor.test.tsx
  Tests  41 passed (41)

❯ vitest run tests/unit/api/field-validation-schema.test.ts   # core
  Tests  10 passed (10)   # 2 failed without the Zod enum change (image, url)

[changeset-bot]

🦋 Changeset detected

Latest commit: d76c937

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 14 packages

Name	Type
@emdash-cms/admin	Minor
emdash	Minor
@emdash-cms/cloudflare	Minor
@emdash-cms/sandbox-workerd	Patch
@emdash-cms/fixture-perf-site	Patch
@emdash-cms/perf-demo-site	Patch
@emdash-cms/cache-demo-site	Patch
@emdash-cms/auth	Minor
@emdash-cms/blocks	Minor
@emdash-cms/gutenberg-to-portable-text	Minor
@emdash-cms/x402	Minor
create-emdash	Minor
@emdash-cms/auth-atproto	Patch
@emdash-cms/plugin-embeds	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

Scope check

This PR changes 542 lines across 9 files. Large PRs are harder to review and more likely to be closed without review.

If this scope is intentional, no action needed. A maintainer will review it. If not, please consider splitting this into smaller PRs.

See CONTRIBUTING.md for contribution guidelines.

[emdashbot]

This is a well-scoped, clean implementation of image sub-fields inside repeaters.

Approach — The change solves the right problem (#1424): repeater rows previously forced every non-scalar sub-field through a plain text input, which made photo galleries painful. Extracting ImageFieldRenderer into its own module to avoid a circular import (ContentEditor → RepeaterField → ImageFieldRenderer) is the correct architectural move, and the component is moved verbatim with no behavior change to top-level image fields.

What I checked

• Diff + full context of all changed files (ContentEditor, RepeaterField, FieldEditor, ImageFieldRenderer, core schema/types, tests, changeset).
• Traced ImageFieldRenderer extraction against the original inline code — verbatim.
• Verified REPEATER_SUB_FIELD_TYPES, the Zod enum in createFieldBody, and the schema-builder select stay in sync and now correctly include both image and the previously missing url.
• Checked AGENTS.md conventions: all new UI strings are Lingui-wrapped, Tailwind classes are RTL-safe (logical end-*, ms-*), no SQL or content-table changes, changeset is present and correctly versioned.
• Confirmed repeater item values still flow through the existing z.unknown() path in the Zod generator — no new validation surface was needed.
• Reviewed test coverage: targeted component tests exercise rendering the picker, showing an existing media-value preview, and initializing new items with null; core tests iterate all whitelisted sub-field types and reject unsupported ones.

Headline conclusion — No bugs, no regressions, no convention violations. The PR is ready to land.

[github-actions]

Overlapping PRs

This PR modifies files that are also changed by other open PRs:

• feat(admin): add date-only content field #1365 (6 shared files)

This may cause merge conflicts or duplicated work. A maintainer will coordinate.

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commit: d76c937

[swissky]

Heads-up on the red Smoke Tests check: it fails in site-matrix-smoke ("all templates and playground build successfully"), which downloads seed images from Unsplash during the build. Every other suite passes on the same commit — Tests, Integration, Browser, all 8 E2E shards, Lint and Typecheck. This PR's core change is purely additive (adds "url" and "image" to the repeater sub-field enums; no template uses image sub-fields), so it can't affect a template build. Looks like a transient network flake on the image download — a re-run should clear it. I don't have rerun permissions here.

[ascorbic]

Thanks!