chore(main): release arize-phoenix-client 3.4.0

[mikeldking]

🤖 I have created a release beep boop

3.4.0 (2026-08-29)

⚠ BREAKING CHANGES

• server: GET /v1/model_providers no longer returns custom providers or a next_cursor, and built-in entries expose provider rather than kind + provider_key. Custom providers move to GET /v1/custom_model_providers. The endpoint is unreleased, so no published client is affected.

Features

• client: add prompt deletion (#15736) (5610755)
• client: record Harbor jobs in Phoenix (#15547) (f7c6cb3)
• client: record Harbor rewards as Phoenix evaluations (#15600) (822d7cb)
• prompts: add REST prompt version creation (#13846) (dbf15e9)
• server: add GET /model_providers REST endpoint (#15561) (59c247a)
• server: add PATCH /projects/{project_identifier}/retention (#15410) (8ffd938)

Bug Fixes

• atif: link system subagents to emitted parent spans (#15585) (22ee343)
• upgrade to anthropic SDK v1 (#15588) (b28cf94)

Performance Improvements

• agents: make the system prompt static and move UI state onto the turn (#15541) (31fafc5)

Miscellaneous Chores

• release arize-phoenix-client 3.4.0 (f8561dc)

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