Add bounded batch parity for embeddings and transcription

[fcogidi]

Summary

• Introduce batch transcription APIs and resilient embedding micro-batching with failure isolation
• Add lazy, bounded batch execution for embedding, and transcription paths with ordered results and per-item callbacks
• Split batch orchestration into private helpers, keep public LMClient methods explicit, and update docs plus benchmark accounting

Testing

• uv run pytest -q
• uv run pre-commit run -a

[Copilot]

Pull request overview

This PR adds bounded/lazy batch execution parity across embeddings and transcription, including resilient embedding micro-batching with per-item failure isolation and per-item callbacks, plus updates to docs and CLI benchmark accounting to match the new behavior.

Changes:

• Refactors embedding + transcription request paths into private helpers and adds bounded batch runners with ordered results and per-item callbacks.
• Introduces transcribe_batch / atranscribe_batch APIs and extends embedding batch APIs with micro_batch_size, on_progress, and on_result.
• Updates CLI embed benchmarking to account for micro-batching/partial failures per vector, and adds tests/docs for the new batch behavior.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/test_client_limits.py	Adds coverage ensuring embedding queue-wait metrics include scheduler delay under bounded admission.
tests/test_client_batch.py	Expands batch tests for embedding failure isolation, callbacks, strict-mode cancellation, and transcription batch behavior.
tests/test_cli_bench.py	Adds benchmark tests for micro-batch sizing propagation and partial-failure accounting.
tests/fakes.py	Extends fake CLI client to record micro_batch_size for embed batch calls.
src/infermesh/types.py	Updates batch-result docs and introduces callback type aliases for batch methods.
src/infermesh/client.py	Wires embedding/transcription through new helpers; adds transcription batch APIs and embedding micro-batch/callback options.
src/infermesh/_transcription.py	New bounded/lazy async transcription batch runner + single-item helper.
src/infermesh/_generation.py	Switches to shared task-cancellation helper for bounded generation batches.
src/infermesh/_embedding.py	New resilient embedding micro-batch runner with recursive failure isolation and per-item callbacks.
src/infermesh/_cli_bench.py	Adjusts embed benchmark accounting to count per-vector submissions/successes/failures; dedupes per-request stats.
src/infermesh/_batch_utils.py	Adds shared cancel_tasks helper for internal batch runners.
docs/guide.md	Documents callback contract parity and new embed/transcribe batch behavior.
README.md	Updates examples and guidance for micro-batched embedding and transcription batch usage/callback parity.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.