refactor(codemode): dispatch all tool calls positionally

[mattzcarey]

Summary

Simplify codemode tool dispatch by treating every sandbox tool call as positional.

Previously providers could opt into positionalArgs, which made the sandbox proxy capture (...args) and made the dispatcher spread those args into the host function. Providers without the flag used a separate single-object path.

This PR removes that split. The sandbox proxy now always captures an argument list and the dispatcher always calls:

fn(...args)

Object-style calls still work naturally because they are just one positional argument:

await codemode.foo({ a, b }) // fn({ a, b })
await shell.writeFile("path", "contents") // fn("path", "contents")

Changes

• Remove positionalArgs from ResolvedProvider and ToolProvider
• Remove ToolDispatcher.positionalArgs
• Use one dispatch path in both Dynamic Worker and iframe runtimes
• Update shell/browser/codemode call sites that used positionalArgs: true
• Rename the TanStack codemode test fixture from .backup.ts to the real test file and merge the existing small TanStack test into it

Verification

npm test --workspace @cloudflare/codemode -- --run
npm run build
npm run check

---

[changeset-bot]

🦋 Changeset detected

Latest commit: 141ea4e

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

This PR includes changesets to release 1 package

Name	Type
@cloudflare/codemode	Patch

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[devin-ai-integration]

Devin Review found 1 potential issue.

View 4 additional findings in Devin Review.

[devin-ai-integration]

🟡 Residual && true in type guard from incomplete cleanup

When removing the positionalArgs validation from isExecuteRequestMessageShape, the old check (provider.positionalArgs === undefined || typeof provider.positionalArgs === "boolean") was replaced with just true instead of being removed entirely. This leaves a dead && true in the .every() predicate at packages/codemode/src/messages.ts:101, which is a no-op but clearly an artifact of an incomplete transformation.

Suggested change

	isRecord(provider) && typeof provider.name === "string" && true
	isRecord(provider) && typeof provider.name === "string"

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commit: 141ea4e

[cjol]

This is very slightly behaviour-changing in edge cases, I think. If args was undefined, we previously sent an empty object, but will now send undefined. Does that matter?

[mattzcarey]

I think I'm happy with this change. feel more correct if everything is positional.

[mattzcarey]

the ai sdk libs would have normalised this anyway. It would only be weird for people doing custom implementation in which case this was broken before so I think I'm actually fine with this being a patch.