Remove the obsolete Pi accounting projection promise
Problem
The Pi README says accounting forwards synchronous callbacks without projecting files. After #508, the harness first awaits a request-scoped prepare handle. Pi prepares the model input through its projector, then the handle shares the prepared input between counting and generation. The sentence therefore makes an inaccurate promise about projection and synchronous accounting.
Design
Remove that one sentence. Keep the accounting requirements for the selected model, serialized input, framing, tools, options and media.
Deletions
One sentence from typescript/packages/pi/README.md; no code changes. This is the README correction split out of #508 for the user's own review.
Tests run
git diff --check passed. Documentation only; the unchanged #508 code retains its passing native, WASM, TypeScript and Windows validation.
Decisions
Leave the human-authorship attestation unchecked. The README guard requires the user's own approval.
Summary by cubic
Removes a README sentence that incorrectly promised Pi accounting forwards synchronous callbacks without projecting files. After the harness change in #508, the request-scoped prepare handle projects the model input before sharing it between counting and generation, so that promise is no longer accurate.
Documentation only; no code changes.