fix(client): enforce sync flush timeout as one end-to-end budget (#3745)

[Anai-Guo]

Problem

Fixes #3745.

The synchronous flush APIs don't enforce timeout as a single end-to-end budget. MilvusClient.flush(collection_name, timeout=N) delegates to GrpcHandler.flush:

• the initial Flush RPC receives the full timeout;
• _wait_for_flushed then starts a new timer and receives the full timeout again;
• the multi-collection path restarts that timer for every collection;
• the poll loop sleeps a fixed 0.5s (5s for flush_all) without capping to the remaining budget.

GrpcHandler.flush_all has the same split-budget behavior between the initial FlushAll RPC and _wait_for_flush_all. A deterministic mocked test with an 8s initial Flush RPC and flush(..., timeout=10) raised its timeout only after ~18.5s of simulated wall-clock.

The async handler is unaffected because its outer retry wrapper bounds the whole coroutine with asyncio.wait_for.

Fix

• Compute one deadline when the public sync call starts.
• Pass the remaining budget to the initial RPC and to every GetFlushState / GetFlushAllState poll.
• Share the same deadline across all collection waits.
• Cap each poll sleep to what is left of the budget.
• Apply the same rule to flush_all.

Tests

New tests/unit/grpc_handler/test_flush_timeout.py:

• test_flush_enforces_end_to_end_timeout_budget — 8s initial RPC + timeout=10; asserts the raise happens within the 10s budget (fails on master, which overshoots to ~18s).
• test_flush_all_enforces_end_to_end_timeout_budget — same for flush_all.
• test_flush_without_timeout_still_waits_until_flushed — timeout=None still polls until flushed and does not raise.

All three pass with the fix; the two budget tests fail on master. The existing test_utility.py flush tests continue to pass.

🤖 Generated with Claude Code

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