First-class async tools; acoustic fillers during long operations

What's Changed

• test: categorize tests and select via pytest --unit/--plugin openai/ … flags by @Bobronium in https://github.com/livekit/agents/pull/5945
• hamming plugin: add customer_metadata, external_links, and session_mode fields by @sumanyu in https://github.com/livekit/agents/pull/5263
• fix(job): log unhandled exceptions in fire-and-forget tasks by @theomonnom in https://github.com/livekit/agents/pull/5961
• ci(deploy-examples): drop manifest publishing job by @theomonnom in https://github.com/livekit/agents/pull/5963
• ci(deploy-examples): deploy from the dispatched branch instead of hardcoded main by @theomonnom in https://github.com/livekit/agents/pull/5964
• feat(voice): flush audio and text output per FlushSentinel by @longcw in https://github.com/livekit/agents/pull/5956
• add ctx.with_filler() for acoustic fillers during long tools by @longcw in https://github.com/livekit/agents/pull/5885
• first-class async tools via ctx.update() by @longcw in https://github.com/livekit/agents/pull/5841
• Deploy examples against the deployed git ref instead of PyPI by @theomonnom in https://github.com/livekit/agents/pull/5969
• feat(job): expose single_peer_connection in JobContext.connect by @renal128 in https://github.com/livekit/agents/pull/5966
• docs: add filler_agent.py to examples README table of contents by @detail-app[bot] in https://github.com/livekit/agents/pull/5967
• docs: update test commands to use pytest category flags by @detail-app[bot] in https://github.com/livekit/agents/pull/5958
• Enable git-lfs in example images so git-installed deps get real LFS binaries by @theomonnom in https://github.com/livekit/agents/pull/5970
• fix(ipc): rate-limit and contextualize high-memory warnings by @Bobronium in https://github.com/livekit/agents/pull/5962
• (examples deploy): fix lfs by @tinalenguyen in https://github.com/livekit/agents/pull/5973
• (openai responses): surface phase field by @tinalenguyen in https://github.com/livekit/agents/pull/5975
• fix(openai): skip empty messages in realtime chat updates by @nightcityblade in https://github.com/livekit/agents/pull/5952
• fix quick reconnect participant keyerror by @tinalenguyen in https://github.com/livekit/agents/pull/5979
• livekit-agents@1.5.18 by @github-actions[bot] in https://github.com/livekit/agents/pull/5981

New Contributors

• @Bobronium made their first contribution in https://github.com/livekit/agents/pull/5945
• @sumanyu made their first contribution in https://github.com/livekit/agents/pull/5263
• @renal128 made their first contribution in https://github.com/livekit/agents/pull/5966

Full Changelog: https://github.com/livekit/agents/compare/livekit-agents@1.5.17...livekit-agents@1.5.18