fix(plugins): route ctx.content seo writes to the SEO panel

[all3f0r1]

What does this PR do?

Fixes ctx.content.create() / ctx.content.update() so plugins can write to the core SEO panel. Previously, passing a seo key in the input failed with SQLite error: no such column: seo because SEO fields live in the separate _emdash_seo table, not on the content row. Plugins could not programmatically populate the SEO panel, which blocked WordPress/Yoast importers, AI-assisted SEO tools, and content automation plugins.

The plugin content adapter now mirrors the REST API behavior:

• createContentAccessWithWrite.create / update extract the reserved seo key from the input and route it to SeoRepository.upsert, running content + SEO writes inside a single withTransaction so either both succeed or neither does.
• Writing seo to a collection without has_seo = 1 throws a validation error matching the REST API (Collection "<x>" does not have SEO enabled).
• createContentAccess.get / list hydrate ContentItem.seo for SEO-enabled collections, so plugins can read current SEO state before doing non-destructive updates (also requested in the issue).
• Partial SEO updates preserve existing fields (via the existing SeoRepository.upsert COALESCE logic).
• A small SeoRepository.isEnabled(collection) helper encapsulates the has_seo lookup used by both the plugin context and the new tests.
• ContentItem, ContentItemSeo, ContentItemSeoInput, and ContentWriteInput are exported from plugins/types.ts so plugin authors get full typings.

Closes #374

Type of change

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

Checklist

• I have read CONTRIBUTING.md
• pnpm typecheck passes
• pnpm --silent lint:json | jq '.diagnostics | length' returns 0 (for files touched by this PR)
• pnpm test passes (2257 tests; 8 new regression tests for [plugins] ctx.content.update() cannot write to seo.* fields (no such column: seo) #374)
• pnpm format has been run
• I have added/updated tests for my changes (if applicable)
• I have added a changeset (if this PR changes a published package)
• New features link to an approved Discussion: https://github.com/emdash-cms/emdash/discussions/... (n/a — bug fix)

AI-generated code disclosure

• This PR includes AI-generated code

Implemented with Claude Code (Opus 4.6). A human reviewed every change, ran the test suite, and wrote the regression tests against the exact repro from the issue. Reviewers may want to pay extra attention to: the transaction boundary in createContentAccessWithWrite.update (the seo-only path intentionally skips ContentRepository.update so it does not bump updated_at/version when only SEO changed — open to flipping this if the project prefers always bumping on any write), and the decision to reserve seo as a magic key inside the flat data map rather than introducing a new envelope shape.

Screenshots / test output

 ✓ tests/integration/plugins/capabilities.test.ts (60 tests) 2081ms

 Test Files  1 passed (1)
      Tests  60 passed (60)

New tests added in packages/core/tests/integration/plugins/capabilities.test.ts under Content Access > SEO panel integration:

• get() returns SEO defaults for SEO-enabled collections
• get() omits seo for non-SEO collections
• update() routes seo to the SEO panel (direct regression test for [plugins] ctx.content.update() cannot write to seo.* fields (no such column: seo) #374)
• update() accepts field updates alongside seo in one call
• update() partial seo updates do not clobber existing fields
• create() routes seo to the SEO panel
• update() throws when seo is provided on a non-SEO collection
• list() hydrates seo for each item in SEO-enabled collections

[changeset-bot]

🦋 Changeset detected

Latest commit: 5d016a5

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

This PR includes changesets to release 9 packages

Name	Type
emdash	Patch
@emdash-cms/cloudflare	Patch
@emdash-cms/plugin-ai-moderation	Patch
@emdash-cms/plugin-atproto	Patch
@emdash-cms/plugin-audit-log	Patch
@emdash-cms/plugin-color	Patch
@emdash-cms/plugin-embeds	Patch
@emdash-cms/plugin-forms	Patch
@emdash-cms/plugin-webhook-notifier	Patch

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

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commit: 5d016a5

[ascorbic]

This is great! Thanks