fix(anthropic): raise default httpx read timeout for streaming; add configurable timeout param

[SuperMarioYL]

Summary

Fixes #5508.

The Anthropic LLM plugin used httpx.AsyncClient(timeout=5.0), which sets all httpx sub-timeouts — including the per-chunk SSE read timeout — to 5 seconds. Claude's adaptive-thinking phases routinely pause for 10–30 s before emitting the first content chunk, so the 5 s read timeout fires during normal usage and raises APIConnectionError, killing voice sessions mid-turn.

Changes

• Default split timeout: httpx.Timeout(5.0, read=30.0) — connect stays at 5 s (genuine TCP failures surface fast) while the per-chunk read window is 30 s (covers standard thinking budgets with headroom).
• New timeout constructor parameter: timeout: httpx.Timeout | None = None lets callers supply a custom timeout without constructing a whole anthropic.AsyncClient — e.g. httpx.Timeout(5.0, read=60.0) for extended thinking or very large contexts. Aligns with the pattern already used by the OpenAI plugin.
• Six unit tests in tests/test_plugin_anthropic.py cover the default split, tight connect value, custom timeout pass-through, and client= precedence over timeout=.

Before / after

# Before — all sub-timeouts at 5 s, kills thinking phases
httpx.AsyncClient(timeout=5.0, ...)

# After — tight connect, generous read
httpx.AsyncClient(timeout=timeout or httpx.Timeout(5.0, read=30.0), ...)

Usage (new parameter)

# Default (30 s read) — sufficient for most models
llm = anthropic.LLM(model="claude-sonnet-4-6")

# Extended thinking or very large contexts
llm = anthropic.LLM(
    model="claude-opus-4-6",
    timeout=httpx.Timeout(5.0, read=60.0),
)

Test plan

• uv run pytest tests/test_plugin_anthropic.py -v — 6/6 pass
• uv run ruff check — no errors
• uv run ruff format --check — no changes needed

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.

[longcw]

looks good to me! something nit:

[longcw]

maybe use NOT_GIVEN

Suggested change

	timeout: httpx.Timeout | None = None,
	timeout: NotGivenOr[httpx.Timeout ] = NOT_GIVEN