Derive test:node and test:bun scope instead of naming test files

[taras]

Problem

test:node and test:bun in the root package.json name individual test files:

packages/durable-streams/tests/*.test.ts
packages/core/tests/{frontmatter,heal,scanner,eval-transform,eval-interpolate,document-output-api,output-normalize,output-terminal}.test.ts

That selection dates from 9db5eae ("chore: add package.json, tsconfig.node.json, and CI matrix for Node"), which introduced Node support. It was a subset even then — packages/core already had 31 test files and 8 were named — and it has only ever been path-renamed since (core/ → packages/core/, ema-api → document-output-api, durable-effects dropped). It has never been re-derived.

The repository now has 81 test files. test:node and test:bun run 19 of them, and 241 of the 930 assertions the Deno suite covers. Nothing signals when a newly-written test is or is not runtime-portable, so the Node and Bun jobs quietly cover less of the codebase every time a test is added.

What the excluded tests actually do

Measured on main at the tip of #142, running each of the 62 excluded files individually and then as a batch:

Runtime	Excluded files that pass unchanged	Fail
Node (tsx)	57 of 62	5
Bun	58 of 62	4

Batch runs of everything except the failures are green in both:

• tsx --tsconfig tsconfig.node.json --test <76 files> → 818 tests, 0 fail (11s)
• bun test <77 files> → 824 tests, 0 fail (18s)

Against today's 241 tests in each job.

Whole packages are currently uncovered by Node and Bun despite passing: all of packages/testing (8 files), packages/acp (5), packages/code-review-agent (3), scripts/tests (1), and 8 of 9 in packages/test-agent.

The genuine divergences

Four files fail in both runtimes, one more only under Node. They look like real cross-runtime defects, not test artifacts, and all sit in the eval / dynamic-import path.

1. import(dataUri) in the eval sandbox — packages/core/tests/eval-context.ts (T18, T19, T20) and packages/core/tests/find-free-port.ts (R6, R1c). Under Node the tsx loader aborts with ERR_INVALID_RETURN_PROPERTY_VALUE: Expected a string to be returned for the "format" from the "load" hook but got null. Under Bun the same tests fail. packages/test-agent/tests/profile.test.ts hits the same loader error under Node but passes under Bun.

2. packages/core/tests/function-components.test.ts FC3 — importing a component fails with No "exports" main defined in .../packages/core/node_modules/remend/package.json. Deno resolves it. Node and Bun both fail.

3. packages/core/tests/expand.test.ts, "component as rejects expression prop" — a behavioral difference, not a harness one. Deno rejects the expression prop with must be a string literal; Node and Bun evaluate it and produce Failed to evaluate expression prop "as={name}" on <Greeting />: name is not defined.

Item 3 in particular means the same document behaves differently depending on the runtime that loads it.

Desired outcome

• test:node and test:bun derive their scope the way deno task test now does (Derive root verification task scope from workspace configuration #140/🔧 chore(tasks): derive root verification scope from workspace configuration #142), rather than naming files.
• A test that is not portable is excluded explicitly, next to a recorded reason, so the exclusion list is short, visible, and reviewable.
• Adding a test file puts it in all three runtime jobs by default; opting out is a deliberate act.

Acceptance criteria

• test:node and test:bun no longer enumerate individual test files.
• The 57/58 currently-passing excluded files run in the Node and Bun CI jobs.
• Each remaining exclusion names the defect it stands in for and is linked to an issue, rather than being silently absent.
• The three divergences above are either fixed or recorded as known runtime limitations with a decision behind them.
• CI and the repository's required verification commands pass.

Note

Deliberately out of scope for #142, which is about package-directory enumeration. These scripts enumerate test files, and widening them needs the decision on the divergences above.