Lightweight render.types route; drop double serializeCard+searchDoc

[habdelra]

Stacked on #4926 (parent ticket CS-11208). Linear: CS-11237.

Summary

• The prerender runner used to call /render/.../meta twice per card. The first call existed only to read the ancestor type chain so the fitted/embedded format renders could be driven; the second captured the real serialized + searchDoc + deps + displayNames after those renders marked linked fields as "used".
• The first call paid for a full serializeCard({includeComputeds:true}) + searchDoc(instance) walk every time, even though the runner consumed only meta.types.
• This PR introduces a sibling host route /render/:id/:nonce/:options/types that returns only the type chain (getClass + getTypes). The runner calls it for the first pass and keeps /meta for the final pass.
• The final render.meta still runs after the fitted/embedded ancestor renders, preserving the isUsed-via-non-isolated-render contract that the non-isolated formats render linked fields and those links appear in search doc test in packages/realm-server/tests/prerendering-test.ts covers.

Why this is safe

The previous attempt in the parent PR collapsed both calls into one and broke that test: a single render.meta before the embedded/fitted renders meant linksTo / linksToMany fields had not yet been marked "used", so the search doc walk missed them. This change does the opposite — it keeps the second render.meta exactly where it was (after the format renders) and replaces only the cheap first call with a route that returns the type list and nothing else.

No new module-state in card-api. No changes required in user realms.

Expected impact

renderElapsedMs per card prerender drops by roughly the wall-clock of one serializeCard + searchDoc on that card type — ~60–80ms for the heaviest cards measured under the parent ticket. Compounds across from-scratch reindex of a multi-file realm.

Test plan

• CI green; in particular non-isolated formats render linked fields and those links appear in search doc in packages/realm-server/tests/prerendering-test.ts passes.
• Local: trigger a from-scratch reindex against a representative realm and check renderElapsedMs distribution shifts down vs. parent branch.

🤖 Generated with Claude Code

[github-actions]

Preview deployments

• Host staging preview

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Host Test Results

    1 files      1 suites   1h 48m 38s ⏱️
2 712 tests 2 697 ✅ 15 💤 0 ❌
2 731 runs  2 716 ✅ 15 💤 0 ❌

Results for commit 4910004.

Realm Server Test Results

    1 files      1 suites   11m 16s ⏱️
1 480 tests 1 480 ✅ 0 💤 0 ❌
1 571 runs  1 571 ✅ 0 💤 0 ❌

Results for commit 4910004.

[Copilot]

Pull request overview

This PR reduces per-card prerender overhead by introducing a lightweight host route that returns only a card’s ancestor type chain, avoiding an extra serializeCard + searchDoc traversal that was previously done solely to obtain meta.types.

Changes:

• Add /render/:id/:nonce/:options/types (host) to return only the ancestor type chain.
• Update the realm-server prerender runner to call render.types for the first pass and keep a single render.meta call for the final (post-ancestor-render) metadata capture.
• Introduce a shared PrerenderTypes payload type in @cardstack/runtime-common.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/runtime-common/index.ts	Adds the PrerenderTypes interface for the new lightweight prerender payload.
packages/realm-server/prerender/utils.ts	Adds renderTypes() capture helper to drive the new /types route.
packages/realm-server/prerender/render-runner.ts	Switches the runner’s first pass from render.meta (types) to render.types.
packages/host/app/templates/render/types.gts	Adds a template that JSON-prints the render.types model.
packages/host/app/routes/render/types.ts	Adds the new host route that computes and returns the ancestor type chain only.
packages/host/app/router.ts	Registers the new render.types route.

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