fix(stagehand): cap the stagehand dependency below the breaking 4.x API

[vdusek]

The scheduled E2E tests fail on every stagehand template job with:

ImportError: cannot import name 'AsyncStagehand' from 'stagehand'

stagehand 4.0.0, released on 2026-08-10, is a breaking API redesign. AsyncStagehand and AsyncSession are gone in favour of a single Stagehand plus Page / Locator, and the whole stagehand.types.session_* module tree that _stagehand_types.py imports was removed. The stagehand extra declared stagehand>=3.19.5 with no upper bound, so the Actor image resolved 4.0.0 and the plugin's top-level import failed, surfaced through try_import as the misleading message above.

Our own CI never saw it, because uv.lock pins 3.22.0 and only the Actor image resolves the dependency fresh. That is also why some stagehand jobs still passed: they reused image layers cached before 4.0.0 was published.

This caps the extra at <4.0.0, matching the existing sqlalchemy[asyncio]>=2.0.0,<3.0.0 style. Migrating the integration to the 4.x API is a separate piece of work.

Verified by mirroring the Actor Dockerfile's pip install ./wheel[stagehand,httpx]: the capped wheel resolves stagehand 3.22.0 and imports StagehandCrawler, StagehandBrowserPlugin, StagehandOptions and StagehandPage cleanly, while a wheel built from master resolves 4.0.0 and reproduces the traceback above.

Failing run: https://github.com/apify/crawlee-python/actions/runs/31583394515

✍️ Drafted by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.66%. Comparing base (091410f) to head (b14d9e4).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2153      +/-   ##
==========================================
+ Coverage   93.51%   93.66%   +0.15%     
==========================================
  Files         181      181              
  Lines       12653    12653              
==========================================
+ Hits        11832    11851      +19     
+ Misses        821      802      -19     

Flag	Coverage Δ
unit	93.66% <ø> (+0.15%)	⬆️

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