Fix page metadata titles without the site-name suffix

[JonahFoster]

What does this PR do?

Fixes shared page metadata title handling so Open Graph, Twitter, and article JSON-LD can use a page-specific title without inheriting the site-name suffix from the document <title>.

Closes #168

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
• pnpm test passes (or targeted tests for my change)
• 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/...

AI-generated code disclosure

• This PR includes AI-generated code

Screenshots / test output

Behavior check:

• Site name remains in the document <title>
• og:title uses the page title without the site-name suffix

Validation run:

• pnpm typecheck passed
• pnpm typecheck:demos passed
• pnpm typecheck:templates passed
• pnpm test passed
• pnpm format run
• pnpm --silent lint:json | jq '.diagnostics | length' returned 0

[changeset-bot]

🦋 Changeset detected

Latest commit: 96c1835

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

[github-actions]

Overlapping PRs

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

• fix: scroll to and focus target field when navigating from visual editing #185 (7 shared files)
• fix: decode URI-encoded slugs for non-ASCII URL support #115 (11 shared files)
• fix(visual-editing): don’t open admin for portableText; simplify starter PT markup #40 (4 shared files)

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